System for receiving communications

ABSTRACT

Methods and systems for spatial filtering transmitters and receivers capable of simultaneous communication with one or more receivers and transmitters, respectively, the receivers capable of outputting source directions to humans or devices. The methods and systems use spherical wave field partial wave expansion (PWE) models for transmitted and received fields at antennas and for waves generated by contributing sources. The source PWE models have expansion coefficients expressed as functions of directional coordinates of the sources. For spatial filtering receivers a processor uses the output signals from at least one sensor outputting signals consistent with Nyquist criteria representative of the wave field and the source PWE model to determines directional coordinates of sources (wherein the number of floating point operations are reduced) and outputs the directional coordinates and communications to a reporter configured for reporting information to humans. For spatial filtering transmitters a processor uses known receiver directions and source partial wave expansions to generate signals for transducers producing a composite total wave field conveying communications to the specified receivers. The methods and communications reduce the processing required for transmitting and receiving spatially filtered communications.

BACKGROUND OF THE INVENTION

The present disclosure relates generally to methods, systems, andconfigurations for receiving communications.

More specifically, the present invention relates to a system for threedimensional multiple signal tracking, and reconstruction for use inconnection with search and rescue, surveillance, storm and severeweather alerting, animal and bird migration, subsurface mapping,anti-terrorism, conventional warfare, etc.

Analog beamforming and antenna steering using loop, parametric and/orphased arrays, are methods employed for direction finding of acousticand electromagnetic waves belonging to quasi-continuous signals. In oneapproach, a directional antenna (such as a parasitic array or loopantenna) is rotated towards the source for maximum reception. Thedetector may be a single receiver, as in the case of electromagneticdevices, or might be human ears receiving the output of two microphonesmounted in the centers of large megaphones. The antenna's ‘beam’ couldalso be steered at a given frequency of operation by artificiallyintroducing appropriate time delays into the detected signals fromdifferent antenna elements. These analog forms of beamforming wereemployed in World War II (radar and acoustics), for tracking aircraftand for transmitter hunting, and traditionally by radio amateurs inhunting hidden transmitters in practice for emergencies for sport, andfor the elimination of undesired signals.

The time of arrival method has also been applied to locating sources ofshort duration signals, such wave pulses generated by earthquakes,shocks, blasts from explosions, cell phones, etc. Time of arrivaltechniques generally seek absolute and arrival time differences betweensignal arrivals at antenna transducer elements. Such systems typicallyobtain information from two or more antennas to obtain directions ofincoming signals and employ triangulation techniques to estimate pointsof origins.

For quasi-continuous signals, certain beamforming and beam steeringmethods use fixed antenna arrays of transducer elements and digitalsignal sampling and processing to convert signal conditioned antennaoutput signals into digitized time series. These methods generally donot require antennas to be rotated, but instead typically make use ofsecond order statistical functions obtained from cross-correlations andcross-spectral densities of time series of the different antennaelements. The second order statistical procedures allow for thedetermination of preferred signal directions and signal power spectra.Artificial channel time delays using digital processing can be used tonumerically steer “antenna beams” and can also incorporate antenna beammodifications for adaptive processing and removal of undesired sources.

In contrast, the present system is based upon the creation andmanipulation of signal vectors providing for the construction ofmathematical models of physical wave fields at or in the vicinity of theantenna.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing, as well as other objects of the present invention, willbe further apparent from the following detailed description of thepreferred embodiment of the invention, when taken together with theaccompanying specification and the drawings, in which:

FIG. 1 is a block diagram of a system constructed in accordance with thepresent invention for a composite acoustic, electromagnetic, and seismicantenna array with self calibration capability;

FIG. 2A is a schematic representation of a spherical microphone antennaconstructed in accordance with the present invention supporting signalvector processing;

FIG. 2B is a perspective view of a cylindrical three dimensional (3D)acoustic array constructed in accordance with the present inventionsupporting signal vector processing;

FIG. 3A is a perspective view, with parts cut away, of a charge densitysampled electromagnetic spherical shell antenna constructed inaccordance with the present invention supporting 3D signal vectorprocessing;

FIG. 3B is a partial perspective view of a capacitive transducerconstructed in accordance with the present invention for samplingelectromagnetic spherical shell antenna surface charge densities atpoints on the surface;

FIG. 4A is a perspective view of a current-sampled electromagnetic 3Dvertical whip antenna constructed in accordance with the presentinvention with ring sub array capable of supporting 3D signal vectorprocessing for elevation angle and bearing determination;

FIG. 4B is a plan view of a sub array ring element constructed inaccordance with the present invention of the antenna in FIG. 4A, whichcan also serve as a planar two dimensional (2D) “bicycle wheel” antennawhen the antenna of FIG. 4A operates in planar mode, or as a stand aloneantenna operating as a 3D antenna in planar mode;

FIG. 4C is a partial perspective view of an inductive transducer formeasuring the electric current at points along the sub array ringelement of FIG. 4B and the rings of FIG. 4A;

FIG. 5A is a schematic representation of a prolate spheroidal shellantenna constructed in accordance with the present invention havingcapacitive and/or inductive transducers supporting 3D operation, planarmodes of operation, signal vector processing and/or possiblyreconstruction of electromagnetic signals; and with microphone and/orhydrophone transducers, could also operate as a submerged and/or towedantenna for scanning sonar and for tracking applications;

FIG. 5B is a schematic representation of a cylindrical shell antennaconstructed in accordance with the present invention having capacitiveand inductive transducers supporting 3D operation, planar modes ofoperation, signal vector processing and/or possibly reconstruction ofelectromagnetic signals; and with microphone and/or hydrophonetransducers could also operate as a submerged and/or towed antenna forscanning sonar and tracking applications;

FIGS. 5C and 5D are a set of partial perspective views of capacitive andinductive transducers, respectively, constructed in accordance with thepresent invention for use on the antennas shown in FIGS. 3-5B formeasuring electric charge and current vector components at selectedpoints on electromagnetic shell antennas;

FIG. 6 is a perspective view of an acoustic “tree” array configurationconstructed in accordance with the present invention and designed toaccount for the coupling of direct and reflected waves by the surface onwhich the antenna is mounted and supporting 3D signal vector processing;

FIG. 7 is a schematic representation of electromagnetic and acousticarrays of the types depicted in FIGS. 2-5B mounted on a vehicle fordeployment in an urban environment and illustrating the application ofthe present invention to locate snipers and cell phones when used with atraceback program;

FIG. 8 is a schematic representation of acoustic and electromagnetic(EM) high density array deployed in accordance with the presentinvention on a vehicle and capable of determining the direction ofincoming fire, of tracking helicopters and/or vehicles, and fordirection finding and tracking of electromagnetic sources such asVHF/UHF hand held radios and cell phones;

FIG. 9 is a schematic representation of farmhouse or barn mounted arraysconstructed in accordance with the present invention for detection ofsevere storms, for providing early warning for tornadoes andthunderstorms, and for announcing the arrival of visiting vehicles;

FIG. 10A is a schematic representation of an active towed transducerarray constructed in accordance with the present invention forapplication as a scanning sonar to 3D image of submerged objects and forallowing observation of objects as the towed transducer arrayapproaches, passes, and departs;

FIG. 10B is a schematic representation of a fixed bottom-mounted orsurface-suspended cylindrical hydrophone array constructed in accordancewith the present invention for monitoring and tracking of shipping,internal waves, and/or tsunamis which may employ hydrophones, geophones,and/or vector magnetometers;

FIG. 11A is a schematic representation of a bottom-mounted hydrophone 3Dtree or spherical array constructed in accordance with the presentinvention for harbor security applications, having both passivedetection and tracking capability (including those capabilitiesreferenced in FIG. 10B) and small boats and swimmer delivery vehicles,depending upon the antenna size and configuration;

FIG. 11B is a schematic representation of a swimmer delivery vehicle anda bottom-mounted cylindrical array constructed in accordance with thepresent invention for applications as referenced in FIG. 10B, and withapplicability to small boats and swimmer delivery vehicles, dependingupon the antenna size and configuration and type of transducer(magnetic, hydrophone, vector magnetometers, etc.);

FIG. 12 is a schematic representation of a mountain deployment of athree dimensional acoustic spherical array constructed in accordancewith the present invention of the type shown in of FIG. 2 , havingbearing and azimuth capability for traffic and/or projectile and/oraircraft tracking and monitoring, and for location of sources, using aincident ray traceback program;

FIG. 13 is a schematic representation of an active and/or passiveseismic array constructed in accordance with the present inventionconsisting of geophones mounted at the end of bore holes drilled intothe mountainside, for permitting mapping and/or monitoring ofunderground facilities;

FIG. 14 is a schematic representation of a combined seismic and/oracoustic array constructed in accordance with the present inventiondeployment for tracking wheeled vehicles, shock waves, and helicopters;

FIG. 15 is a schematic representation of calibration electronicsconstructed in accordance with the present invention showing a signalgenerator, coupling to transducers, amplifiers, A/D converters, andprocessor;

FIG. 16 is a perspective view of a single channel acoustic transducerdriver constructed in accordance with the present invention for anoperator-supported calibration, for which calibration can be carried outone channel at a time;

FIG. 17 is a plan view of a multiple channel acoustic transducer driverconstructed in accordance with the present invention for simultaneousmultiple channel calibration;

FIG. 18 is a schematic representation of an example dual purpose sevensensor acoustic and/or seismic sensor array constructed in accordancewith the present invention with supporting signal conditioning unit,sample geophone, microphone, and computer for in-field processing;

FIG. 19 is a schematic representation of a transducer positioncalibrating method of the present invention using a field survey andapplicable to large scale antennas whose transducer locations may havebeen altered by environmental events;

FIG. 20 is a block diagram of an embodiment of the system constructed inaccordance with the present invention operating in transmission mode;

FIG. 21 is a schematic representation of a planar array constructed inaccordance with the present invention operating in 3D mode capable ofproviding elevation and bearing information on incoming signals;

FIG. 22 is a schematic representation of an 3D antenna constructed inaccordance with the present invention having a collection of 2Dsubarrays operating in planar modes and capable of providing elevationand bearing information on incoming signals;

FIG. 23 is a schematic representation of a 3D hemispherical antennaconstructed in accordance with the present invention having a collectionof 2D planar subarrays operating collectively in either 3D mode orindividually in 2D mode with 3D capability and in either case capable ofproviding elevation and bearing information on incoming signals whenmounted on a planar surface with known acoustic properties;

FIG. 24 is a schematic representation of a formation of airplanesparticipating in simultaneous directed communication using a systemconstructed in accordance with the present invention;

FIG. 25 is a schematic representation of a computer network having aserver connected to a system constructed in accordance with the presentinvention in transmission mode and configured to permit simultaneousdirectional communications with several logged on clients;

FIG. 26 is a schematic representation of a system constructed inaccordance with the present invention illustrating a field operativemaintaining simultaneous directional communication with several stationswith reduced risk of eavesdropping by outsiders;

FIG. 27 is a schematic representation of a system constructed inaccordance with the present invention illustrating a ship maintainingsimultaneous directional communication with several satellites and/orstations with reduced risk of eavesdropping by outsiders;

FIG. 28 is a schematic representation of a system constructed inaccordance with the present invention illustrating a bird trackingapparatus for reporting flocks of large birds to an airport tower;

FIG. 29 is a schematic representation of a system constructed inaccordance with the present invention illustrating a bird monitorreporting the presence of vocal birds to a bird watcher or one trackingthe migration of vocal flocks of birds;

FIG. 30 is a schematic representation of a system constructed inaccordance with the present invention illustrating a diagnostic tool formonitor sounds within the human body;

FIG. 31 is a schematic representation of a system constructed inaccordance with the present invention illustrating simultaneous commonchannel communication between a stationary tower and two movingvehicles;

FIG. 32 is a schematic representation of a seismic (and possiblyacoustic) system constructed in accordance with the present inventionfor monitoring and reporting the presence, speed and, potentially, thetype of a vehicle traveling along a road;

FIG. 33A is a schematic representation of a system constructed inaccordance with the present invention for receiving a spatiallyencrypted message from two transmitter (or for the simultaneousreception of to independent messages);

FIG. 33B is a schematic representation of a system constructed inaccordance with the present invention for transmitting a spatiallyencrypted message to two receivers (or for the simultaneous reception ofto independent messages);

FIG. 34 is a schematic representation of a system constructed inaccordance with the present invention for the conveyance of a spatiallyencrypted message from a transmitter to a receiver via two linkedreceiver-transmitter pairs;

FIG. 35 is a schematic representation of a system constructed inaccordance with the present invention illustrating a cross-section ofthe propagating shock wave front and various directions and anglesassociated with the trigonometric determination of the range to a sourceof a supersonic ballistic projectile created by a muzzle type blast;

FIG. 36 is a schematic representation of a system constructed inaccordance with the present invention illustrating how a singleembodiment of the present invention can be applied to the problem ofdetermining the direction and range to a sniper firing at groundpersonnel;

FIG. 37 is a schematic representation of a system constructed inaccordance with the present invention illustrating how an activeembodiment of the present invention consisting of a coupled transmitterand receiver operating in a “sonar” type mode can be employed fordetecting the presence of intruders in the environment of a building;

FIG. 38 is a schematic representation of a system constructed inaccordance with the present invention illustrating how anelectromagnetic embodiment of the present invention acting in a “radar”mode can be used to plot positions of aircraft on or in the presence ofan airport without the radar beam scanning as with conventional radars;

FIG. 39 is a schematic representation of a system constructed inaccordance with the present invention illustrating how an activeacoustic embodiment of the present invention operating in a “sonar” modecan be used to detect the presence of “silent” intruders in a harborenvironment without the sonar scanning as with conventional radars;

FIG. 40A is a schematic representation of operation of a systemconstructed in accordance with the present invention for determinationof a projectile's trajectory, miss distance, and velocity using anantenna array;

FIG. 40B is a schematic representation of operation of a systemconstructed in accordance with the present invention illustratingincident and reflected rays defining a plane of approach for arrival ofa reflected shock wave;

FIG. 41A is a schematic representation of a system constructed inaccordance with the present invention for extracting messages, orcommunications, of generally simultaneous spectrally competitivecomponent fields generated by resolvable transmitters;

FIG. 41B is a schematic representation of a system constructed inaccordance with the present invention for generating a composite fieldfor sending generally simultaneous spectrally competitive communicationsto corresponding resolvable receivers; and

FIG. 42 is a schematic representation of a system constructed inaccordance with the present invention for increasing the spectralefficiency of a cellular phone system.

FIGS. 43A-C are schematic representations of a system constructed inaccordance with the present invention for a communication receivingsystem capable of spatial filtering and determining the directions andcontent of multiple simultaneous sources;

FIG. 44A is a schematic representation of a system constructed inaccordance with the present invention for a spatial filtering receivingcommunication system capable of processing simultaneous communications;

FIG. 44B is a schematic representation of a system constructed inaccordance with the present invention for a spatial filteringtransmitting system capable of conveying simultaneous communications toone or more receivers,

FIG. 45A is a schematic representation of another example implementationof a system constructed in accordance with the present invention,including an antenna structure with multiple transducers placedconsistent with Nyquist criteria;

FIG. 45B is a schematic representation of an example implementation of aprocessor or receiver suitable for use with the antenna shown in FIG.45A;

FIG. 45C is a schematic representation of an example implementation of atransducer suitable for use with the antenna shown in FIG. 45A andincludes a ring passing through a toroid supporting a coil;

FIG. 46A is a schematic representation of an example implementation of asystem for receiving communications from a source of a physical wavefield using transducer signals generated by a physical wave fieldgenerating fluctuations within a structure; and

FIG. 46B is a schematic representation of an example implementation of asystem for transmitting multiple communications via a physical wavefield using transducers to generate fluctuations within a structure inturn generating the physical wave field carrying the desiredcommunications to receivers.

SUMMARY OF THE INVENTION

Generally, the present invention includes a method and apparatus fordetermining selected information from signals contained in a physicalwave field, the properties of the physical wave field being detectableover three spatial dimensions and a temporal dimension, and the methodincluding characterizing the physical wave field by a signal vectorproviding a mathematical model of the physical wave field, anddetermining the selected information from the signal vector. The presentinvention also provides further embodiments for reconstruction ofspectrally competitive signals and their simultaneous transmission intodifferent resolvable directions, such signals being receivable at one ormore destinations while minimizing substantive interference by the othersignals being simultaneously transmitted.

The necessary equations, theory, and computational tools required forconstructing embodiments of the present invention for the differentphysical wave types are historical and well known and can be establishedusing the following texts (which are incorporated herein by reference):Stratton, Electromagnetic Theory, 1941 Chap 9; Jackson, ClassicalElectrodynamics, 1962 Chapter 16; Roger G. Newton, Scattering of Wavesand Particles, 1966; (Jenkins and White, Fundamentals of Optics, 1957);Thorne Lay & Terry C. Wallace, Modern Global Seismology, 1995; andOppenheim and Schafer, Digital Signal Processing, 1975; Mathworks,Matlab and Signal Processing Toolbox (User's Guides), 1998; Roman,Theory of Elementary Particles, 1961; Balanis, “Antenna Theory Ayalysisand Design: 2005, John Wiley and Sons; The ARRL, “The ARRL Antenna Bookfor Radio Communications”, 23′ Edition” and “The ARRL Handbook for RadioCommunications 2008”, The American Radio Relay League, Newington, Conn.;and Milford, Foundations of Electromagnetic Theory, John Wiley and Sons,1960. As a consequence the details of these theoretical notions,equations, and the standard mathematical tools (Mathworks) are notdiscussed in detail herein.

The general natures of the approaches of the present invention areapplicable to linear physical wave types or those which can besufficiently treated as linearized waves. Because of the large number ofapplications of the invention to different physical media and wavetypes, for the sake of brevity, illustration of specific applications ofthe preferred embodiment are limited herein to several demonstrativeacoustic, seismic, and electromagnetic applications, and it is to beunderstood that the present invention is not to be limited to theapplications and embodiments disclosed herein.

The conceptual basis for the present invention lies in properties ofsolutions to scalar and vector field wave equations describing physicalwave propagation in different physical media and/or in the fieldsinduced by such propagating waves in certain material media. Themathematical models chosen determine the available information. Thechoice of which physical wave fields are of interest, the propagatingwave and/or the waves it induces on surfaces, depends upon whattransducers are employed and what is required to attain the desiredselected information in the given situation. Under proper circumstancespropagating wavefields in the vicinity of a spatial surface aredetermined by sufficient knowledge of wave fields and their derivativeson that surface over some time interval (see Jackson or Stratton).Kirchoff Surface-Integral representations provide such connections (thetreatment of diffraction is such an example) and so can the waveequation itself (with sufficient knowledge of the field along thesurface power series expansions can be defined to define themathematical model in the vicinity of the surface). With these cases,more extensive selected information can be obtained. In other cases, theability to construct a mathematical model on the surface itself maysuffice. Whatever the choice for selected data, data collection of bandlimited signals through discrete spatial and temporal sampling usingproperly selected transducers placed along such a surface according towell understood criteria can provide the required information, as theNyquist sampling theorem shows. The signal vector is either a collecteddata set containing such required sample information or the equivalent,and therefore contains all the information obtainable from the chosenmathematical model. The selected data, considered already established asobtainable from the field, can be extracted then from signal vectors orthe chosen wave fields through the data reduction procedures describedbelow.

Depending on the nature of the embodiment's antenna, what is beingsampled via data collection, the choice of transducers, and the natureof desired selected data, signal vectors can characterize physical wavefield fluctuations and/or fluctuations in physical “charge” and“current” density fields on surfaces. The latter can arise inelectromagnetism. Thus, the signal vector characterization of anincoming wave field can be indirect. The type of signal vector for themost extensive selected information is that dictated by the proceduresfor mathematical wave field model determination in the antenna vicinity,as described above, for knowledge of the most complete description ofthe propagating wave field implies knowledge of the most completeinformation.

The present invention includes, in certain embodiments, systems andmethodologies using antenna arrays of transducer elements, together withelectronic signal processing hardware, signal conditioning units, signalprocessing software, and reporting electronics. The present inventionincludes a method of deriving signals obtained from properly configuredantenna elements (transducers or sensors) which convert acoustic,seismic, fluid dynamic, electromagnetic and/or electric charge orcurrent density wave fluctuations into fluctuating voltages or currents.These signals are amplified and filtered as necessary, and thendigitized. The resulting time series of the signals constitute a signalvector providing for the construction of a mathematical representationof the physical wave chosen over the bandpass of interest. The signalvector is cast in representation or form suitable for attainment ofdesired selected information. The signal vector is then manipulated fordesired selected data and/or to obtain the signal vectors characterizingfields of resolved sources of incoming signals. A reversal of theprocess provides for the construction of a mathematical model for thesignals generated by fields of resolved sources using their individuallycharacterizing signal vectors, from which the information content theycarry can be determined through digital signal processing and/or throughproper digital to analog (“D/A”) conversion and demodulation.

Pre-constructed libraries of directional and/or modeling signal vectorsand the superposition principle enable the determination of desiredsignal information from data processing algorithms. In essence, the goalof being able to approximately construct the individual signals ofresolved sources of interest as they would be received at the antenna,as if each such resolved source was the only signal present, serves asthe most basic design criteria for embodiments of the present inventionoperating at the highest level. The path to the goal permits theincorporation of new techniques for the extraction of selectedinformation (including that of detection, tracking, and modulationcontent) and the development of new criteria for when such informationis obtainable. However, the system of the present invention can operatewithout reaching the above-stated goal in the event of partial hardwarefailure or breakage, when conditions and desired selected data allow arelaxation of system configuration constraints, or when the chosenmathematical model is not necessary for the attainment of certainselected information.

There are additional fundamental application independent notionsunderlying the concept of the apparatus or invention. One such notion isthat hardware/software/processor configurations and the dimensionalityof the vector space in which the signal vectors are defined are coupledto the resolving power specifying the ability to differentiateneighboring signals having identical frequencies. Yet another is thatantenna sensors can be configured and sampled such that for a givenfrequency bandpass their time series constitute sufficient data to allowdetermination of a signal vector representing the incoming field.Another is that different equivalent representations for a signal vectorcan be chosen, such as those (but not limited to) of the temporal,frequency, and partial wave domains, the choice being applicationdependent. Another fundamental notion is that signal vectors of anydomain can be linearly and quasi-linearly manipulated for noisereduction and for the attainment of selected information, including butnot limited to, that for detection, tracking, and the classification ofmultiple spectrally competitive sources. The superposition principleapplies to signal vectors as well as to the wave fields. Another is thatthe library element signal vectors of preconstructed libraries can beused to construct the individual signals of resolved sources, and thatthose of overlapping data set time segments can be merged to provide fordetermination of the information content of such signals within theoperating bandpass. However, certain elements of desired selectedinformation may not require complete construction of the signal vectorsof each source making up the sampled signal vector. A general reversalof this process used for such reconstruction, allowed by the linearnature of the procedure, allows for simultaneous transmission ofindependent selected information in multiple spectrally competitivesignals into directions that can be resolved by the system.

Different applications of the invention to different wave processesrequire certain changes in hardware components. For example, foracoustic waves in air, microphones could be employed as antennatransducer elements. For acoustic waves in water, hydrophones could beemployed, and for seismic waves, the antenna elements would be geophonesor vector magnetometers, as would also be the case for tsunamis. Forelectromagnetic waves, inductors could be employed or capacitors mountedon or in metallic surfaces. For oceanic internal waves, the transducersmight be thermistors and/or magnetometers. Correspondingly and dependingupon wavelength and frequency, different signal conditioning and dataacquisition units could be used. When necessary, a single mixer may beused to simultaneously lower the frequency of the incoming signals onall channels so that the relative phase and amplitude characteristics ofthe signals of antenna sensor elements are preserved and samplingrequirements reduced. The construction of a signal vector requiresproper choices for antenna sensor placement and configuration, thefrequency bandpass to be sampled, computational word size, and themechanism for determining the signal vector of a chosen representationjointly typically define an embodiment of the present invention.However, given an application, once the signal vector has beendetermined, the procedures for computation of selected information arenearly independent of the physical type of application. The possibleembodiments of the invention include composite systems capable ofsimultaneously handling all three classes of physical phenomena, as wellas a data reporting system possibly using the utility's antennastructure as part of a microwave or RF transmission remote reportingsystem.

Scalar products between signal and library vectors and constructs of thelatter provide for classes of selected information, depending upon thesignal to noise ratio and the system resolving power. Signal vectors asrepresentatives of physical wave fields models can be differentiated toobtain the derivatives of the physical wave field model they represent,providing other procedures for obtaining selected information. A numberof possibilities exist for obtaining selected information from signalvectors as representatives of physical wave fields.

The identification and detection process also provides bearing andelevation angles of individual sources. Multiple source tracking anddifferentiation is based upon the resolving power of the embodiment. Anadaptive noise based metric tensor characterizing the environmentalnoise background redefines scalar products to provide for the adaptiveremoval of unwanted and interfering sources and a map between apparentand true estimates for directions of incoming signal waves, alleviatinga beam maintenance problem found with adaptive beamforming approaches.The linear nature of the physical wave field to signal vectormathematical map enables signal enhancement through signal vectoraveraging and the attainment of relatively high resolving power throughuse of high element density arrays and/or a consequent reduction innumerical processing demands.

The system can incorporate use of digitized contour maps of theenvironment. Such digitized data permits incoming signal directions tobe traced back to their points of origin when such tracebacks intersectphysical surfaces characterized in digitized contour maps. In this way,range and source location can be determined from individual antennas.When antennas large enough to measure wavefront curvature are employed,and wavefront curvature is incorporated as a library category, range canalso potentially be determined. When neither of these procedures can beutilized, source range can be determined from triangulation techniquesusing more than one system of the present invention with baselines ofproper length, while Doppler observations can be used to estimatetrajectory directions and closest points of approach. The presentembodiment also permits range to a source to be determined from a singleantenna in certain circumstances.

The system can incorporate calibration and self-testing for verificationof performance criteria. The self calibration and self-testingcapabilities allow for automatically switching to alternate modes ofoperation, with perhaps some reduction in signal detection and resolvingcapability, should some signal channels become damaged or disconnected.

Using subsets of predetermined signal vector libraries, threedimensional systems can be operated in two dimensional modes whenincoming signals have their wave propagation vector in a common plane.With a 3D system, this can be done in any plane. Thus, with the systemof the present invention, optimum performance may be obtained for wavespropagating parallel to the surface of the ground even if the antennamast is not vertical. The 3D algorithms can be used with 3D subsetlibraries to operate high transducer density 2D antennas in 2D modes.The present invention can use its antenna structure for housing utilityelectronics and microwave remote reporting gear and also have it serveas a radio or TV transmitting antenna.

Given a chosen bandpass, the accuracy of the underlying mathematicalmodel is determined by the accuracy of the sampling, the level of systemelectronic noise, the level of environmental random noise, and signalprocessing accuracy, and how well data sampling criteria are met.Environmental considerations, the physical process, the anticipatedscenario, and operational constraints may dictate the choice of antennatransducer system to be used. Each embodiment should preferably employ aself consistent configuration, so that the system outputs reliableselected information to a reporter for decision making by a human orother external device.

The present invention also includes, in one embodiment, a method andsystem and/or apparatus for determination of a projectile's trajectory,miss distance, and velocity using an antenna array.

The present invention additionally includes, in one embodiment, a methodand system and/or apparatus for extracting communications of generallysimultaneous spectrally competitive component fields from resolvabletransmitters.

The present invention further includes, in one embodiment, a method andsystem and/or apparatus for relaying simultaneous and spectrallycompetitive communications from a set of transmitters on a commonchannel and rebroadcasting such signals over another channel toresolvable receivers generally as a second composite field.

The present invention also includes, in one embodiment, a method andsystem and/or apparatus for increasing the spectral efficiency of acellular phone system.

In exemplary implementations of the present disclosure, methods andsystems are provided for determining and outputting communications froma source contributing to a wave field, and include providing thedirectional coordinates of the source and an antenna structure having atleast one transducer consistent with Nyquist criteria for the wave fieldand generating signals representative of the wave field at thetransducer. A wave field partial wave expansion (PWE) model is providedcomprised of wave field partial wave functions (PWFs) and unknowncorresponding PWE coefficients as is also a source PWE coefficient modelconsistent with the wave field of the source at the antenna structurecomprised of source coefficients expressed as functions of thedirectional coordinates of the source. Additionally, a library of PWFsevaluated at the location of the transducer is included, wherein outputsignals are received from the transducer, and the transducer outputs atleast one output signal consistent with Nyquist criteria representativeof the wave field. Using a processor, the at least one output signal,and the library of PWFs, at least one of the unknown PWE coefficients isdetermined, and using the source PWE coefficient model, the directionalcoordinates of the source, and the at least one of the determinedunknown PWE coefficients at least one communication from the source isdetermined for output to a human or device, wherein the number offloating point operations required to be performed by the processor todetermine and output the communications from the source are reduced.

In other exemplary implementations of the present disclosure, methodsand systems are provided for determining and outputting communicationsfrom a source contributing to a wave field, and include providing thedirectional coordinates of the source and an antenna structure having atleast one transducer consistent with Nyquist criteria for the wave fieldand generating signals representative of the wave field at thetransducer. A test source partial wave expansion (PWE) model is providedconsistent with the wave field of the source at the antenna structurecomprised of source coefficients expressed as functions of thedirectional coordinates of the source. Also provided is a test libraryof test source partial wave functions (PWFs) evaluated at the locationof the transducer. Output signals from the transducer are received andsignals are output consistent with Nyquist criteria representative ofthe wave field. And, a processor uses the at least one output signal andthe test library to coefficients to determine at least one communicationfrom the source for output to a human or device, wherein the number offloating point operations required to be performed by the processor todetermine and output the communications from the source are reduced.

In still other exemplary implementations of the present disclosure,methods and systems are provided for transmitting a communication to areceiver in a wave field, and include providing at least one signalconveying the communication and an antenna structure having at least onetransducer consistent with Nyquist criteria for the wave field andgenerating the wave field at the transducer for communicating to thereceiver. A transmitting partial wave expansion (PWE) model is providedconsistent with boundary conditions of the antenna structure andcomprised of known coefficients for supporting directed communicationsto the receiver and expressed as functions of the directionalcoordinates of the receiver. A transmitting library consisting oftransmitting PWE models evaluated at the location of the transducer isincluded. A processor communicatively coupled to the transducer isconfigured for using the at least one signal and the transmittinglibrary to send at least one communication signal to the transducer andto use the transducer to convey the at least one communication to thereceiver, wherein the number of floating point operations required to beperformed by the processor to convey the at least one communication tothe receiver are reduced. In example implementations of the presentdisclosure, a method is provided for determining at least one directionto or outputting communications from at least one source contributing toa source wave field, where the method includes providing an antennastructure with multiple transducers placed consistent with Nyquistcriteria along a closed surface and generating signals representative ofa wave field at the transducers. A signal selection device monitors thesignals of each of the transducers, and a model is provided for beampatterns associated with the transducers. A processor analyzes dataoutput by the transducers, and detection criteria determine the presenceof signals at each transducer. Using the signal selection device, thedata output by the transducers, the detection criteria, and theprocessor communications are determined and output from sources incidentwithin a sector defined by the detecting transducer's beam pattern,thereby allowing for a reduction in the number of floating pointoperations required to be performed by the processor for determining atleast one direction to or outputting communications from at least onesource.

In example implementations of the present disclosure, a system isprovided for determining directions to and outputting communicationsfrom at least one source contributing to a source wave field, and thesystem includes an antenna structure having multiple transducers placedconsistent with Nyquist criteria along a closed surface and generatingsignals representative of the wave field at the transducers. A signalselection device is configured to monitor the signal of each transducerand for outputting signals, and a processor is configured for analyzingdata output by said transducers. At least one transmission link islinked to the signal selection device for conveying the signals outputby the selector devise to the processor, and beam pattern models areprovided for the beam patterns associated with the transducers. Adetection criteria is used for determining the presence of signals ateach transducer, and means are provided for using the beam patternmodels to determine sectors monitored by each transducer, wherein thesignal selection device, the transducer output signals, the detectioncriteria, and the processor are configured to allow communications to bedetermined and output from sources incident within a sector defined bythe detecting transducer's beam pattern, thereby allowing for areduction in the number of floating point operations required to beperformed by the processor for determining at least one direction to oroutputting communications from the at least one source.

In example implementations of the present disclosure, a method isprovided for determining and outputting communications from at least onesource contributing to a source way field, the method encompassingproviding an antenna structure with multiple transducers placedconsistent with Nyquist criteria along a closed surface and outputtingsignals representative of the field at the transducers and providingdetection criteria for determining the presence of signals at eachtransducer. A transducer selection device is configured to monitor thesignals of each of the transducers, and the method includes providing areceiver for converting the signals output from the transducers intocommunications. The method further includes using the signal selectiondevice, transducer output signals, detection criteria and receiver todetermine and output communications from sources incident within atransducer's sector, thereby allowing for a reduction in the number offloating point operations required to be performed by the processor fordetermining at least one direction to or outputting communications fromthe at least one source.

In example implementations of the present disclosure, a system isprovided for determining and outputting communications from at least onesource contributing to a source way field, where the system includes anantenna structure with multiple transducers placed consistent withNyquist criteria along a closed surface and configured for outputtingsignals representative of the field at the transducers. A detectioncriteria allows determination of the presence of signals at eachtransducer, and a transducer selection device monitors the signalsoutput by each of the transducers. A receiver is configured forconverting the output signals of said transducers into communications,and means are provided for using the signal selection device, transduceroutput signals, detection criteria and receiver to determine and outputcommunications from sources incident within a transducer's sector.

In another implementation of the present disclosure, a method isprovided for determining directions to and outputting communicationsfrom at least one source contributing to a source wave field in apropagating medium. The method includes providing a structure placedwithin the propagating medium, the structure incorporating multipletransducers whose output channels output simultaneous signals consistentwith temporal and spatial Nyquist criteria that represent andcharacterize fluctuating charge and current densities within thestructure. The method includes providing a directional model defining amap between the direction to each possible source in the propagationmedium and a set of output signals created by the fluctuating charge andcurrent densities generated by the waves emanating from each possiblesource in the propagation medium, and further includes providingdetection criteria for determining the presence of signals from at leastone source in the propagation medium in each output channel.Additionally, the method includes providing a sector model constructedfrom the directional model and detection criteria, the sector modeldefining collections of possible source directions and collectionweights for each output channel, and also, providing a processorcommunicatively coupled to the signals from the output channels andconfigured for analyzing their signals. The method further comprisesusing the processor, the signals from the output channels, the detectioncriteria, and the sector models collections and weights to identifyprobable collections of directions possibly containing the at least onesource in the propagation medium and/or outputting the communicationsfrom the at least one source.

Additional implementations of methods of the present disclosure mayinclude the antenna structure including parasitic elements and/or beingmetallic and the charge and current densities being electric current andcharge densities, respectively, and/or the antenna structure being ofmetallic material and the charge and current densities are mass currentand density fluctuations, respectively.

Moreover, implementations of methods of the present disclosure mayinclude restricting consideration of incoming directions to thosecontained in the identified possible collections of directions and usingthe processor, signals from the output channels, the directional model,and the identified collections of probable directions to determine thedirections to and communications from at least one source, to therebyreduce the time and processing required to obtain the selectedinformation.

Further implementations of the present disclosure may include a systemfor determining directions to and outputting communications from atleast one source contributing to a source wave field in a propagationmedium. The system includes a structure placed within the propagatingmedium, the structure incorporating multiple transducers whose outputchannels output simultaneous signals consistent with temporal andspatial Nyquist criteria that represent and characterize fluctuatingcharge and current densities within the structure. A directional modelis provided defining a map between the direction to each possible sourcein the propagation medium and the set of output signals created by thefluctuating charge and current densities generated by the wavesemanating from each possible source. Detection criteria is provided fordetermining the presence of signals from at least one source in thepropagation medium in each output channel, and a sector model isconstructed from the directional model and detection criteria, thesector model defining collections of possible source directions andcollection weights for each output channel. Additionally, a processor iscommunicatively coupled to the signals from the output channels andconfigured to use the signals from the output channels, the detectioncriteria, and the sector model collections and weights to identify andoutput probable collections of directions possibly containing the atleast one source in the propagation medium and/or outputting thecommunications from the at least one source.

Implementations of the present disclosure may include a system where theantenna structure is metallic and the charge and current densities areelectric current and charge densities, respectively, and/or where theantenna structure includes parasitic elements and/or is metallicmaterial and the charge and current densities are mass current anddensity fluctuations, respectively. Additionally, the processor may beconfigured to restrict consideration of possible directions to those ofthe identified collections of possible directions, signals from theoutput channels, and the directional model to determine the directionsto and communications from at least one source, to thereby reducerequired processing time and system energy requirements.

In another implementation of the present disclosure, a method isprovided for outputting communications to at least one receiver via aphysical wave field in a propagation medium, where the method includesproviding the directions to the at least one receiver and providing astructure placed within the propagating medium, the structureincorporating multiple transducers generating consistent with temporaland spatial Nyquist criteria fluctuating charge and current densitieswithin the structure from the transducer input signals. The methodfurther includes providing a directional model relating input signalsets to the propagation directions of consequent fields generated bysaid fluctuating charge and current densities within the structure andproviding a sector model constructed from the directional model, thesector model defining collections of possible receiver directions andcollection weights for each channel. Additionally, the method includesproviding a processor communicatively coupled to the structure's channelinputs and configured for generating their signal, and using theprocessor, the directions to at least one receiver, at least onepossible channel input signal and the sector models collections andweights to output communications to the at least one receiver.

Other implementations of the present disclosure may include a system foroutputting communications to intended receivers via a wave field in apropagating medium, where the system includes providing the directionsto at least one receiver and a structure placed within the propagatingmedium, the structure incorporating multiple transducers generatingconsistent with temporal and spatial Nyquist criteria fluctuating chargeand current densities within the structure within from the transducerinput signals. A directional model relates sets of structure inputsignals to the propagation directions of fields generated in thepropagating medium by the structure's charge and current densityfluctuations. A communications interface is provided for the intendedreceivers, and a processor is communicatively coupled to the structure'stransducer channel inputs and configured for generating their inputsignals, the processor being further configured to use the receiverdirections and the directional model to generate the channel inputsignals needed to convey the communications to the at least onereceiver.

In example implementations of the present disclosure, an antennastructure may include parasitic elements, array elements which are notdriven by transducers.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The foregoing, as well as other objects of the present invention, willbe further apparent from the following detailed description of thepreferred embodiment of the invention, when taken together with theaccompanying drawings and the description which follows set forth thisinvention in its preferred embodiment. However, it is contemplated thatpersons generally familiar with mathematical wave propagation models andwith communications and direction finding systems and their theory willbe able to apply the novel characteristics of the structures illustratedand described herein in other contexts by modification of certaindetails. Accordingly, the drawings and description are not to be takenas restrictive on the scope of this invention, but are to be understoodas broad and general teachings.

It is to be noted at the outset that the present disclosure herebyincorporates by reference in their entirety the following U.S. Patents:U.S. patent Ser. No. 10/690,744; U.S. patent Ser. No. 10/495,719; U.S.Pat. Nos. 8,542,555; 7,679,998; 7,782,710; 7,643,377; 7,394,724;7,423,934; 7,372,774; and 7,123,548.

Referring now to the drawings in detail, wherein like referencecharacters represent like elements or features throughout the variousviews, the high resolution, vectorized three dimensional multiple targettracking and signal reconstruction system of the present invention isillustrated in various embodiments.

The general structure of the physical components of the presentinvention is described below, as is the basis for the realization ofsignal vectors, stated with examples. Also described is the basis forconfiguring embodiments constructed in accordance with the presentinvention and procedures for obtaining selected information.

The overall structure of one preferred signal reconstruction anddirection finding system, generally 10, constructed in accordance withthe present invention is depicted in FIG. 1 . Transducers 12 ofantennas, such as acoustic antenna AC, electromagnetic antenna E, and/orseismic antenna S, convert physical wave fluctuations at the location ofeach transducer into electrical fluctuations. Mixer and signalconditioning units, generally SCU, can amplify, filter, and mix thesignals of each transducer as requirements dictate. The SCU outputs arethen passed to analog-to-digital converters, generally A/D, to digitalfilters, generally DF, operating consistent with temporal Nyquistsampling criteria (Oppenheim and Schafer). Further signal processingtakes place in an array processor AP (or computer CPU, possibly aparallel processor) on time series data output from the A/D converters,and/or digital converters DF, and data reduction take place undersoftware. The array processor AP feeds a reporter, generally RPTR, fortransmission of results on selected information in suitable form tohumans.

System 10 is illustrated having acoustic, seismic, and electromagneticcapability. It includes software for an optional calibration signal feedrunning from the computer processing unit AP through a calibratingsignal generator, generally CSG, to transducers 12. The software for thesignal calibration feed provides signals for calibration of the system10 and for verification of system performance within allowed tolerances.The above system in diagram 10 can also be used with an appropriatehydrodynamic sensor (not shown) for use in detecting hydrodynamicwavefields.

Although FIG. 1 only illustrates applications for acoustic,electrodynamic, and seismic wave types, possible solutions and wavetypes can include scalar, vector, and tensor fields associated withcoordinate systems appropriate for different possible antenna symmetriesand physical processes (acoustic, seismic, electromagnetic, andhydrodynamic) and environmental conditions. Each such model isassociated and consistent with implementation of the conceptual basisfor the embodiment as described in the above Summary as applied to thepertinent type(s) of physical wave propagation, or consistent with anincomplete implementation if the desired selected information allows.

The propagating physical wave and the detected or transducer sampledphysical wave may differ. For example, if the propagating wave iselectromagnetic, the transducer detected wave may be that of electriccharge and current densities on the surface of a conductor as induced bythe propagating wave. Mathematical models used in accordance with thepresent invention provide the map between sampled data and the chosenphysical wave fields to model.

The present invention includes procedures for obtaining signal vectors.Transducers can be considered as placed upon a surface, real orimaginary. The type of transducers utilized should be consistent withthe chosen mathematical model for the chosen physical wave field beingsampled. The transducers should preferably be small compared withrelevant wavelengths, so that measurements can be associated withspecific transducer locations on the transducer surface. If transducerspacing, number, and the temporal sampling rate for wave fieldfluctuations meet Nyquist sampling criteria for waves on that surface,then the mathematical representation for the wave fluctuations ispreferably uniquely determined over that surface for the period data iscollected. Furthermore, even if a choice is made for completemathematical model for the incoming wave field, and transducer type andsampling is consistent with this choice, a mathematical model for thefield can also be determined within the vicinity of that surface. Hence,a proper discrete set of samples can define a signal vector, and theFourier Transforms of these temporal sample sets can also define signalvectors.

Signal vectors can also be obtained as expansion coefficients of partialwave expansions (PWEs). The latter are defined by separable or nearlyseparable solutions to wave equations defining the mathematical modelsfor the relevant physical wave fields, those formed through the processof separation of variables. Each partial wave is labeled by theseparation constants defining it. For a properly configured system, thesignal vectors defined by expansion coefficients of suitably truncatedpartial wave expansions are equivalent to those described above, and canbe related by mathematical transformation. Integral forms for solutionsof wave fields, such as those developed by Sommerfeld and Weyl(Stratton) can also be used to define signal vectors.

The procedures allowing for the construction of a chosen mathematicalmodel for a physical wave field in the neighborhood a surface followfrom knowledge of the field and required spatial and temporalderivatives on the surface, and mathematically established uniquenesscriteria for the field's mathematical model tell what is required.Nyquist criteria tell when a sufficient number of samples at asufficient number of spatial locations are taken for a given bandpassand time period. Consequently, with sufficient temporal sampling ratesthe model for the chosen physical wave field everywhere on the surfacecan be constructed, and the field on that surface can be numericallydifferentiated, so that temporal Fourier transforms in time are alsoknown thereon in principle. For certain choices physical wave fields andmathematical models and types of transducers, implied knowledge ofspatial and temporal derivatives along the surface allows constructionof the wave field model in the neighborhood of the surface, when thelatter is needed as selected information. The dispersion relation givingwave number as a function of frequency is known from the wave equation,so the maximum number of wavelengths present along the surface can bedetermined for each frequency (considering various possible directionsfor incoming waves). This determines required antenna transducer spacingaccording to the sample criteria and the angular resolving power aswell, which is given by the angular aperture of the shortest possiblewavelength along the surface, a result consistent with Lord Rayleigh'scriteria for “just” resolution in optics (Jenkins and White).

The sample theorem is not the only basis for obtaining a map between asignal vector and the physical wave the old that it represents. Forexample, the signal vector could define a mathematical model of aphysical wave field using a least-squares or other non faithfultechnique for establishing partial wave expansion coefficients of apartial wave representation of physical wave field in an antennaneighborhood. In such case, spatial and temporal Nyquist criteria neednot be fully met. In the latter case, obtained selected informationcould be ambiguous or non unique.

Signal vectors can be the ordered set of samples (time series data)collected from the transducers via A/D conversion over some temporalwindow. Signal vectors also can be the set of Fourier coefficientsobtained discrete Fourier transforms of this time series data. Or, theycan be the expansion coefficients of a suitably truncated partial waveexpansion (associated with a coordinate system for which the waveequation is separable). Other signal vectors can also be obtained, forexample, from a discretization of integral solutions to a wave equation.For all such cases, the set of signal vector components will besymbolically represented by S_(α) and the signal vector by s, where α isa collective index.

The signal vector index α differentiating components of the signalvector may characterize the set jt_(k) of the original samples (j labelsthe transducer where the sample at time t_(k) was taken), as such, itcharacterizes the original sample set time series. It may alsocharacterize the frequencies and transducer label of the Fouriertransformed time series data. In the case of partial wave expansion, itcharacterizes the indices labeling the distinct partial waves, such asthe traditional (k,l,m) of the expansion for spherical partial waves,etc. Thus, the signal vectors component indices may result from thereshaping of a signal tensor. The particular choice of signal vectorrepresentation depends upon the selected information being sought andthe nature of the environment in which the system is to be used. Forexample, for sources at long range, the plane wave PWEs provide a usefulsignal vector representation for spectral components of incomingsignals, while spherical wave PWEs are useful for descriptions of samein spherical polar coordinates when output for bearing and elevationangles of sources is desired.

For a carefully configured embodiment the different signal vectorrepresentations are equivalent, a situation occurring when embodimentresolving power, temporal and spatial sampling, and hardware processingare consistent. The Fast Fourier Transform (FFT) relates the spectraldomain signal vector to that of the temporal domain. The partial wavefunctions (PWFs) evaluated at transducer locations define thetransformation from one of the former to one of the partial waverepresentations of a signal vector. In fact the spectral domain signalvector is that of a partial wave expansion in harmonic functions. Theaforementioned representations of signal vectors are of courseequivalent to some specifiable accuracy, for example, the accuracy withwhich the truncations of the infinite PWEs are valid, or that to which alow pass filter is effective in meeting Nyquist sampling criteria.

The mathematical description of a physical wave field may be amulti-component entity, as with seismic and electromagnetic waves. Inthe latter case, the signal vectors may be obtained through electric andcurrent vector densities on a metallic surface. The Kirchoff typerepresentations and associated uniqueness theorems for each choice offield for which an embodiment is to be constructed provides a guide towhat data need be sampled. The same information can be obtained throughconsideration of what is required to create a power series expansion forthe mathematical model using the wave equation. Use of the wave equationand proper temporal and spatial application of the sample theoremprovide the latter. For a complete specification of a mathematicalmodel, depending on desired selected data, more than one type oftransducer may be required (for example, through use of both velocityand pressure sampled microphones in acoustics, capacitors and/orinductors in electromagnetics). Seismic and hydrodynamic waves treatablewith linear mathematical models exhibit analogous properties.

The choice for a signal vector representation should preferably be madeon the basis of numerical efficiency in obtaining the selectedinformation and upon the dictates of the appropriate uniquenesstheorems. The most efficient are typically those for which thecoordinate system reflects the symmetry of the antenna system andenvironment and for which the wave equation allows for the separation ofvariables. Example antennae of such “efficient” systems are illustratedin FIGS. 2-6 .

If the antenna presence significantly disturbs the propagation of thephysical wave, then the model solution to the wave equation for waves ofeach incoming direction should preferably include the scattered wave aswell. The signal vector should preferably as much as possiblecharacterize the total wave field of both the incoming and scatteredwave, as required by the selected information sought, for accurateresults.

The antenna is the physical device containing transducers through whichthe fluctuations of the physical wave or induced “charge densities” areconverted into electrical fluctuations. The specific form of theconversion process is assumed to be understood and linear, so that thesuperposition principle applying to composite waves of multiple sourcescan be tracked in the electrical fluctuations. Transducers define a mapbetween physical wave field fluctuations Ψ and voltage or currentfluctuations σ.

After amplification, A/D conversion, signal conditioning, and digitalbandpass filtering, any decimation, and possible Fourier transform (viaFFTs) of properly windowed time series from each transducer channel,various representations of the signal vector are obtained from linearequations of the form:

${\sigma_{A} = {{\sum\limits_{\alpha}{s_{\alpha}K_{A}^{\alpha}j}} = 1}},\ldots,N_{s}$In this signal vector equation, σ_(A) may be proportional to the A^(th)component of the wave field, as might be in the acoustic applicationwith use of microphones, or to surface charge or current densitycomponents, as in the electromagnetic case (related to the normalcomponents of the electric field and the tangential components of themagnetic field at a conducting surface, respectively). The coefficientmatrix elements K_(A) ^(α) may coincide with the identity matrix if thesignal vector represents the samples themselves, or may be the partialwave functions evaluated at transducer locations in the case of PWErepresentations of the signal vector.

Antennae with microphone transducers may be used for sensing pressurefluctuations (FIGS. 2A, 2B, and 6 ), with capacitive transducers forsensing surface charge densities (FIGS. 3A, 3B, 5A, and 5B), and withinductive transducers for sensing surface current densities (FIGS. 4A,4B, 4C, 5A, and 5B). For the acoustic case, depending on the level ofmathematical model the signal vector should define, the transducersmight include both pressure and velocity type microphones. In theelectromagnetic case, antennas may combine capacitive and inductivesampling using capacitive transducers 54 and inductive transducers 56.In the latter case when the two types of transducers 54, 56 are takentogether, sampling would allow the polarization of incoming waves to beaddressed as selected information and also allow field reconstructiongiven proper scattering models for the antenna structure. For thecapacitive electromagnetic antenna of FIG. 3A, only the surface chargedensity sampled by transducers 34 of FIG. 3B, related to the normalcomponent of the electric field at the surface, is required fordetermination of the directions of incoming waves, as an analysis ofelectromagnetic vector partial wave solutions can show. However, ifsignal reconstruction and or polarization information is required,additional sampling may be needed, as with using the inductivetransducers of 56 of FIG. 5D, or a combination of one inductivetransducer 56 and one capacitive transducer 54 set therein. Note thatany of the antenna shapes may be used for acoustic or electromagneticsampling in FIGS. 3A, 4A and 4B, and in FIGS. 5A and 5B and FIG. 6 .

Other possible transducer types not specifically illustrated in theFIGS. above include hydrophones (sampling acoustic pressure fluctuationsin fluids), geophones (sampling displacement velocities in seismicmedia), total field magnetometers (sampling magnetic fluctuationsparallel to the earth's magnetic field), vector magnetometers (samplingfluctuations in the magnetic field components), and thermistors(embodiments sampling temperature fluctuations of oceanic internalwaves). Magnetometers can also indirectly sample magnetic fluctuationsin oceanic tidal, internal, tsunamic, and surface waves. The presentinvention is not limited to these types; it can be used with anytransducer set sampling entities associated with waves mathematicallymodeled by linear equations. The transducers should preferably, however,be relatively small in comparison to the shortest wavelength envisionedin the process, so that samples may be associated with points on theclosed transducer surfaces. Antennas with open surfaces may also beclosed using suitable spatial windowing techniques analogous to thoseused in temporal sampling.

Depending upon whether the dimensionality of the signal vector coincideswith the number of transducers utilized (generating utilized datachains) there exists a number of numerical methods that can be utilizedfor the inversion of the signal vector equation (Math works). FastFourier transforms, and matrix inversion and least square techniqueshave been employed in embodiments to invert the truncated partial waveexpansions of different coordinate systems and physical waves. However,if the inversion process is not one-to-one, then there can be ambiguityin any subsequent signal reconstruction, with a potential for subsequentloss of information.

The system configuration sets the resolving power, the size of theantenna, the number of required transducers, and the dimensionality ofthe signal vector. A minimal configuration provides for the minimumnumber of transducers allowing for the definition of a signal vector(the number of its effective independent components thereof), asrequired by the Nyquist criteria, and as discussed above this alsoestablishes the resolving power. The latter, according to Rayleigh'scriteria for “just resolved” follows when the maxima of a surface waveof one source is at the first null of that of another, a criteriadeveloped for consideration in optics when two sources are present. Thecriteria coincides with the minimal condition set by the Nyquistsampling criteria, that there must be at least one transducer for eachhalf wavelength along the surface. Here, we define the embodiment'sresolving power, generally RP, is defined as the minimum number ofresolvable sources on any closed circle centered on the antenna, thenumber being viewed as a function of such circles. More generally, theresolving power can be obtained from the signal vector/mathematicalphysical wave field model map, if maps are obtained by techniques otherthan that based upon the sample theorem, or through use of a signalvector library, as discussed below.

Assuming that any incoming direction is possible, the maximum projectionof the wavevector k corresponds to the shortest wavelength at any pointon the surface. Then, according to Rayleigh's criteria for “justresolved”, the resolving power is: RP=2kR. But, this is just twice thenumber of wavelengths around the imaginary circle. Accordingly, theNyquist criteria also establishes Ns=2kR as the minimum number ofrequired transducers to be uniformly aligned on such a circle, or thenumber needed per unit length if the transducer surface is not made ofcircles. Ns also coincides with the utilized dimensionality of thesignal vector required for the highest frequency considered for a givendirection, also according to the sample theorem. For a sphericalsurface, the number of required transducers and signal vectordimensionality is then (2kR)² if the resolving power is independent ofloop orientation. If not every incoming direction is possible, theuniformity requirement for resolving power can be relaxed.

The considerations on resolving power and number of required sensorsrefer to the σ_(A) of the signal vector equation for a scalar field. Forvector and tensor fields, the result may differ. For electromagneticwaves, if the embodiment is needed to carry out a complete signalreconstruction, the number of required sensors is twice that above, asthere are two polarizations. The result is then that of a sum over thetwo polarizations, which would be the same as that for a scalar field.Note that for propagating electromagnetic waves not all three of thecomponents of the electric and magnetic fields are independent.

Data reduction consists of determining the selected information desired.It involves detection, direction finding, source classification throughspectral decomposition, and signal reconstruction. It makes use of thesuperposition principle, pre-constructed libraries of mathematicalmodels of possible sources, and certain geometrical entities. The latterinclude scalar products, signal surfaces, energy surfaces, detectionsurfaces, and adaptive directional maps.

The superposition principle regards the signal vectors s of receivedcomposite signals as the sum of those of possible sources s_(q) andnoise. This applies to any form of the signal vector, whether in thesample, frequency, partial wave, or integral form domains.

The most fundamental signal vector library is the directional library(DL), which is created and developed from signal vectors of possibledirections and frequencies within the bandpass of interest. Let s_(k)denote such a library element, the wavevector k corresponding to theincoming wave spherical polar angle direction (θ_(k), ϕ_(k)). Such alibrary can form the set of signal vectors of point sources at very longrange, so that the modeled incoming waves are plane when they pass overthe embodiment's antenna or are solutions to a scattering probleminvolving boundary conditions. The directional library can beconstructed using analytical models and/or numerical models.

A signal surface is the surface defined by scalar products|between thesignal vector of the sampled wave and library elements with the incomingsignal vector for all wave directions k. The “radial” coordinate foreach point on the surface corresponding to a DL element is the value ofthe scalar product corresponding to that direction of k. The metric forthis scalar product is that which is appropriate for the signal vectorrepresentation. For the sample and frequency domains representations,the metric is diagonal, and each such diagonal element has unit value.

To each signal surface there corresponds an “energy surface” denoted bys²=|s(θ_(k), ϕ_(k))|². Note that each library element can have its own“signal surface”, defined by scalar products of the form (s_(k),s_(k′))for all possible wavevector directions k′. Each such element alsotherefore has its own “energy surface” s_(k) ².

The “adaptive signal surface” is obtained by weighting the value of thesignal surface for the direction of k by the inverse of the average ofthe noise background signal energy surface for the same direction, theaverage being taken over a number of temporal windows or realizations.

The adaptive signal surface is a distorted signal surface so that thedirection associated with maxima in the signal surface's energy surfacemay not define the cor-rect direction to a source. The “noise adaptivesignal surface” reduces the contributions of noise sources to the signalsurface for directions for which the average noise background is largerelative to other directions. Such noise sources may include knownsources whose presence is also known and understood but not of interest.Thus, the adaptive signal surface procedure is particularly useful forreducing the effect of background interference from known sources not oftracking interest. In such instances where distor-tion exists, anadaptive map should preferably be used to obtain the true directions forvectors associated with sources. This map will be defined below.

There are two classes of detection criteria. One is energy detection,appropriate for the situation when only a single source of interest isknown to be present, or the source is already known to be well resolved,and the signal-to-noise ratio is good. The second is that of directionaldetection, useful when the presence of multiple sources are suspected oranticipated, the sources may not be all resolved, and/or when the signalto noise ratio is low.

There are also different levels to be reached in declaring a detection.The first is that of a probable detection. A probable direction ispreferably automatically assigned to every detection. The notions forprobable detection and probable direction apply regardless of whetherthe signal surface utilized is adaptive or not.

Energy detection is a threshold detection based upon the energy surfaces² (θ, ϕ). If the maximum value for the latter as a function of (θ, ϕ)exceeds that of the averaged noise background “energy” by somepreassigned number, then a probable detection is declared. Thepreassigned number can be based upon a false alarm rate following from amodel for expected detections from some noise model.

Directional detection utilizes signal and library direction vector raydirection properties. With directional detection, signal vectors(including directional library vectors) are normalized such that theirsignal surfaces have value unity for the direction for which thecorresponding energy surface has a maximum value. A probable detectionis declared if the absolute value of the difference surface resultingfrom the difference between the signal surface of the incoming wavefield and that of a directional vector integrated over all directions topoints on the difference surface is below some threshold. Thus, thedetection is based upon a model for the shape of the signal vector of agiven source, instead of upon the signal level relative to somebackground and threshold.

For energy detection, the directions of the probable sources are thosefor which the signal energy surface has maximum values exceeding thethreshold. For directional detection, the assigned probable direction isthat for which the total “energy” of the difference surfacecorresponding to a particular direction vector has its minimum value.Probable directions associated with the adaptive signal surface arepreferably assigned only after the adaptive map is employed.

The adaptive map transfers the directions assigned to sources of signalsurfaces constructed using the adaptive scalar product to truedirections. The directional criteria can result in the signal surfaceand adaptive signal surface assigning different directions to the sameincoming signal detected if the time averaged noise background “energysurface” is not isotropic. The map can be computed off line by notingthe adaptive signal surface directions assigned to the modeled incomingplane wavevector directions used to define the directional libraryvectors using the two metrics, and constructing a table lookup for thiscorrespondence.

For “energy detection,” the direction assigned to the probable detectedsource is that of the maximum of the signal surface, the value of (θ, ϕ)belonging to the vector k of the s_(k) defining the signal surfacemaxima. This assignment can be made to other maxima provided those areat least just resolved, according to the criteria discussed above.

For directional detection, the assigned direction is that belonging tothe s_(k) producing a minimum value for the signal vectors satisfyingthe criteria for probable directional detections, provided the minimumis at least just resolved from other minima.

If multiple sources are encountered, it is preferable to ascertainwhether they are resolved, and if so, incorporate the resolvingcapability into the detection criteria. A local resolving power as afunction of direction is ordinarily readily determined.

The local resolving power is found by observing the functionaldependence of the scalar product (s_(k), s_(′)′) and determining theangular separation γ_(RP) between the directions for which this scalarproduct has its maximum value and its first minimum away from thiscentral maxima. The local resolving power is then defined by:LRP=2π/γ_(RP), where γ_(RP) is the angle just described, hereafterreferred to as the resolving angle. Conceptually, LRP is typically anestimate of the number of equally spaced sources that could be resolvedalong a circle. For a two dimensional transducer surface, the localresolving power can be defined as the geometric mean of the localresolving powers for two orthogonal directions.

The detection rate surface is the surface defined by the rate at whichdetections occur per unit solid angle, as defined by probabledirections, the rate determined over a number of data collectionwindows. Noise interference effects generate detections even whensources of interest may not be present. The detection surface forbackground noise alone is denoted by DR_(N), and in the presence ofsignals of interest, by DR_((S+N)). The detection rate surfaces ofprobable detections can be defined after a sufficient number ofrealizations has taken place to yield a sufficiently smooth function ofthe spherical and polar angles.

Detection measure surfaces provide for the declaration of a detectedsource. One such measure could be the surface defined by the noiseaveraged detection ratio (DR_(S+N)−DR_(N))/(DR_(S+N)+DR_(N)). Thisdefinition requires that a number of realizations be employed to computethe average, and that the ratio be considered a function of angle.

Declaration of a detected source is made if the measure function ofdirection has maxima exceeding a detection threshold (DT); if the shapeof the maxima is judged consistent with noise properties; and if theangular distance between such maxima is consistent with the embodiment'sresolving power. Thus, the concept of resolving power plays a role inthe declaration of multiple source detections.

In some instances, such as when the “energy” (in the sense discussedabove) is sufficient and only one source is known to be present, adetected physical source can be declared directly. The detectionmeasure-based procedure can potentially permit detection at thebackground level less the antenna array gain, even when multiple sourcesare present.

Signal averaged detection follows from a different process. It isparticularly applicable to impulse signals such as those of projectileshock and blast waves, and in estimating the directions of continuoussignals with identifiable spectra, such as those associated withharmonic chains of piston engines.

For impulse waves belonging to short duration single occurrences, thedetection rate surfaces and temporal averaging processes described abovemay not be particularly useful. But such impulse signals are broadbandin nature, and the signal surfaces can be averaged over frequency. Thenoise fluctuations of the different frequencies have different signalsurface oscillation wavelengths, which average out in the summationprocess, while the surface functions at their maxima are normalized tounity and add coherently within the resolving angle. In this type ofaverage, the normalized signal surfaces (normalized by their maxima asdescribed above) are summed and divided by the total number of spectralcomponents involved. Either the energy detection or directionaldetection (appropriately modified) process can be applied to the result,the averaging process also can be limited to frequencies having probabledetections. This technique has been found to yield excellent results indetecting gunfire and shooter directions, as well as those shock wavesassociated with the projectile. It will also be useful in the trackingof turbine engines, which also have broad band spectra. The detectionrate surface process could also be applied to the spectrally averagedsignal surface if the events are repetitive.

In the case of piston engine harmonics, the signal averaging summationis carried out only for elements of the harmonic chain. This is a usefultechnique since the Doppler shift of elements of the harmonic chainyields another harmonic chain (with different spacing for chainelements) and direction finding, and detection of individual elements ofthe chain may not yield accurate results if the signal levels are toolow. Again, the signal surfaces involved must be normalized to unity inthe direction they have their maxima.

For sources at very long range, or for where they are at rest, or whentheir directions are changing little with time, the properly normalizedsignal surfaces could be averaged over data collection temporal windows.Also, an average over both temporal windows and frequency could be made,depending upon the anticipated nature of the sources and theenvironment. Again, detection rate surfaces based detection criteria areapplicable.

If the noise based adaptive signal surface is used in signal averageddetection, it should preferably first be mapped into a standard signalsurface using the adaptive map for each frequency before signalaveraging takes place, if the noise background changes with time. Thisis because the signal surfaces of different frequencies may havediffering distortions.

The choice of which signal detection process is used depends upon theanticipated signal to noise ratio, whether or not the signal has broadspectral content or a harmonic chain, and the duration of the signal.The signal surface averaging processes are particularly useful becausethe effects of random sources and fluctuations generated by randomprocesses affecting paths tend to average to zero, in sharp contrastwith averages involving “energy” type functions. Source directions comewith the detection processes.

For noise averaged detection, the assigned direction are the maxima ofthe detection rate measure surface meeting the detection measurethreshold, provided the maxima is at least just resolved from othermaxima as per the discussion on noise averaged detection above.

For signal averaged detection, the direction assigned is that of themaxima of the signal averaged signal surface exceeding some threshold,as with directional detection. There can be more than one such directionif there is more than one maxima exceeding the detection threshold,provided the maxima involved are just resolved.

For noise averaged signal averaged detection, the assigned direction isthat of the maxima in the measure surface. There can be more than onesuch assigned direction if there are other maxima meeting the detectionthreshold criteria, provided those maxima are at least just resolved.

Source spectral content is established once the s_(q) have beendetermined for a resolved source. Given the s_(q) weighted of theircontributions as defined by the scalar products defining signalsurfaces, the s_(q) can be transformed to the frequency domain. Thefrequency domain s_(q) coincides with the Fourier coefficients of theincoming time series data of the q^(th) source, and its spectra isdefined. This amounts to executing the signal vector equation with theσ_(A) as the result and the weighted s_(q) as input. The resulting|σ_(A)|² then provides the power spectra. The source level of aparticular source q can be estimated from a propagation model for thegiven environment, taking into account attenuation and geometricalspreading.

Signal reconstruction and signal information content are carried out bytransforming from the derived representation for the weighted frequencydomain s_(q), and then using the inverse Fourier transform (discrete) togo to the equivalent sample representation of the s_(q), This must becarried out for a series of overlapping temporal data collectionwindows, where in the set of field values τ indexes the sample set orsample window of the j^(th) transducer at the listed coordinates foreach time t_(k) of the window. If this is done for a series ofoverlapping temporal windows, windowing functions W (t_(k)−τ) can beemployed to construct from these sets a smooth time series over anextended time period. This process permits determination of informationcontent or reconstruction of received signals using digital signalgenerators carrying out digital to analog conversion, provided theembodiment bandwidth is sufficient for the resolved signal and allsignificant spectral components of the resolved signal are included.

If the proper set of transducers are employed in conjunction with thewave equation or surface integral expressions of the Khirkoff type, asper associated uniqueness theorem criteria, a mathematicalrepresentation of the field in the neighborhood (or vicinity) of theantenna can be carried out. In this case selected, information can beobtained after the mathematical model of the wave field has beenconstructed from obtained signal vectors. This can be done using thewell known Neother's theorem techniques applied to mathematical modelLagrangians to obtain energy and momentum vector densities (Roman)explicitly carrying directional and frequency content.

Note that it is not necessary to temporally sample at twice the highesttransmitted frequency to get desired modulation information as selectedinformation. The processed signal need only be heterodyned and sampledat a rate of at least twice the highest modulation frequency, since thesignal vector equation can be scaled so that all the transducer signalsare sampled relative to one.

Several example embodiments and deployments are illustrated in FIGS.2-14 , but it is to be understood, however, that the present inventionis not limited to the examples and embodiments herein disclosed.

For each antenna illustrated, transducer spacing depends upon thedesired resolving power, which should be compatible with the number oftransducers allowed. The resolving power need not be the same for alldirections.

For a spherical antenna having spherically symmetric resolving power,the Nyquist criteria requires N_(s)=(2kR)²=(LPR)². The partial wavesdefining signal vector components can be the spherical harmonic-basedset of consisting of the j_(l)(kR)Y_(lm)(θ, ϕ), where

j_(l) denotes the Bessel function, Y_(lm) the spherical harmonics, k isthe wavenumber, and R is the spherical radius. The signal vector index αconsists of the indices k, l, and m for each frequency. The series istruncated for a maximum value. The Fourier and spherical harmonicrepresentations for the signal vector are equivalent. Near equal angularspacing of transducer elements can be achieved by having element planeswith near equal polar angle spacing containing groupings of (2l+1)transducers, equally spaced within.

The spherical antenna, generally 22, of FIG. 2A is of the type which isappropriate for acoustic microphone transducers obeying these placementrules. The insert in FIGS. 2A and 2B indicates generally how theelectronics, such as SCU, A/D, DF, AP, and RPTR, can be mounted withinthe mast. With thin structural elements and transducer dimensionsrelative to a wavelength, it has not yet been found necessary to includethe influence of the element scattered waves on the transducers. Othercoplanar grouping of transducers could involve √{square root over(N_(s))} equally spaced transducers in √{square root over (N_(s))}planes, with equal polar angle spacing, but the result does not givenear uniform resolving power for all directions.

For the cylindrical antenna 30 of FIG. 2B, the partial waves consist ofproducts of ordinary Bessel functions of the radial coordinate, theexponential function along the axis, and harmonic functions for thebearing coordinate, if a cylindrical partial wave representation is usedto define a signal vector. This antenna would require windowing in theaxial coordinate in order to simulate the condition that a closedsurface contains the transducers, since practical systems cannot beinfinite in length. A maximum spacing of λ/(2 sin(φ)) betweentransducers is preferably required along the cylinder's axis, where λ isthe wavelength at the highest frequency and φ is the highest anticipatedangle of elevation over the plane of a ring. For a bearing resolvingpower of LRP=2ka, the number of microphones along equally spaced ringsshould be equal to or larger than 2ka, where k is the wave number of thehighest frequency to be studied and a is the cylindrical radius, andconsistent with the above, 2ka such rings 26 should be used at aminimum. Note that the first and last ring need not be at the “ends” ofthe cylinder where the windowing function vanishes. With this type ofconfiguration, generally there is an equivalence between the Fourier andcylindrical partial wave representations of the signal vector.

FIG. 3A illustrates a spherical electromagnetic antenna, generally 32,with capacitors, generally 34, whose construction is illustrated in FIG.3B, having an insulator 38 and another plate 39. Capacitors 34 can haveone capacitive transducer plate being the surface 36 of the highlyconducting metallic spherical shell. The same transducer placementconsiderations apply as discussed for FIG. 2A. The capacitor's impedanceover the bandpass should be consistent with electronics and samplingrequirements on time constants, and the capacitors should preferably besmall in comparison to a wavelength. At cell phone frequencies, suchantennas are capable of high density transducer placement and resolvingpower and portable for placement with individuals or on vehicles.

FIG. 4A is an electromagnetic cylindrical ring antenna 40, theelectromagnetic counterpart of the antenna of FIG. 2B. The transducersare inductors 42 as illustrated in FIG. 4C and are equally spaced onrings 44 (FIG. 4B). The inductors 42 are insulated windings over thehighly metallic ring surface 46, as illustrated in FIG. 4C. Inductoraxial and angular placement is the same as the transducer placement asper the discussion on FIG. 2B. The inductors should preferably also besmall in comparison with utilized wavelengths and their electronicimpedance should be consistent with electronic impedance requirementsover the bandpass. At cell phone and other high frequencies, suchantennae can have high density, high resolution, and be mounted as“whip” antennas above vehicles.

Use of high density antennae also permits adaptive reduction of vehiclenoise using the adaptive noise metric, as discussed above, or noisereduction using Gram-Schmidt orthogonalization applied to the signalvectors. Such antenna when mounted as tall structures could potentiallysupport highly accurate systems for measuring elevation angle as well asthe bearings of low elevation angle incident radiation. Note that thistype of structure, with microphones or hydrophones replacing inductors42, also can be used as acoustic systems in air and water. In the lattercase, when embedded in the ground with hydrophones, as in a well, theycan be used to map noises in underground facilities, when propermodeling and boundary conditions are employed. If the overall antennaedimensions of FIGS. 4A and 4B are small compared to utilizedwavelengths, antenna scattering need not be accounted for in acoustics,but must be accounted for in the electromagnetic case when metallicsurfaces are utilized. Some scattering models exist in the literaturereference above.

FIGS. 5A and 5B depict an ellipsoidal, or prolate spheroidal, antenna,generally 50, and a cylindrical shell antenna 52, respectively,associated with separable coordinate systems and also capable ofsupporting PWE based signal vectors. They can be used with hydrophonesfor water applications, with microphones for acoustic applications inair, with capacitive transducers 54 as in FIG. 5C, or with inductivetransducers 56, as shown in FIG. 5D. In the case of inductors, with two“polarizations” for the inductive transducers as 55 in FIG. 5C, such anantenna can determine the polarization of incoming waves and be used forelectromagnetic signal reconstruction, as discussed above.

With the antennae 50, 52, and the spherical shell antenna 32 of FIG. 3A,the modeling library signal vectors should include shell scatteringeffects for both electromagnetic and acoustic waves. If desired, theelectromagnetic transducers could be replaced with acoustic microphones.

A theoretical analysis shows that the signal vectors of incomingelectromagnetic waves at long range are characterized by the expansioncoefficients of vector spherical harmonics, so that capacitivetransducers suffice if the desired selected information is confined totracking information. The sampled charge and current densities are thoseof signals including the possible polarizations. If the selectedinformation also requires wave polarization information or individualsignal source reconstruction, then preferably, the complete set oftransducers 54, 56 depicted in the FIGS. 5C and 5D can be employed. Thespherical antenna would use spherical Bessel functions and vectorharmonics for its vector partial wave expansion, while the ellipsoidalantenna 50 could use “corresponding” prolate spherical coordinates andfunctions. If the minor axis of the ellipse is chosen to be the onerotated about, then the oblate spheroidal coordinates and thecorresponding PWE would be used. The complete number of requiredtransducers 54, 56 is double the number required in the acoustic casefor the spherical antenna of FIG. 2A for the same wavelength, aconsequence of the two polarizations. In any case, transducer spacingshould preferably be determined by the maximum projection of thewavevector for the highest frequency onto the surface containing thetransducers 54, and the spacing should preferably be less than or equalto half the length of the shortest corresponding projected wavelength.

Supporting electronics can be built into the antenna masts and/orspheres and/or ellipsoids as desired. Such antennas are very practicalfor electromagnetic frequencies running from short wave and VHF to cellphone frequencies. The spheroidal antenna 50 would use vector wavesolutions as well, but would employ cylindrical vector harmonics as inStratton (referenced above), the vector harmonics and the vector wavesolutions involving derivatives of the aforementioned functions.

With the capacitive antenna, the transducers 54 and 34 sample surfacecharge densities on the surface, while with the inductive antennasurface, surface current densities are sampled. Complete scatteringsolutions for incident plane waves with the proper polarizations canyield the necessary connection between incoming fields of sources atlong range and induced surface charge and current densities. Theconnection is defined by well know boundary conditions relating thesurface charge and current densities to the normal components of theelectric field and the tangential components of the magnetic field. Forthe electromagnetic antennas mounted on the metallic surfaces, thecapacitive and inductive transducers should also have dimensions andstructure compatible with the impedances required by the electronics andsampling criteria, i.e., time constants associated with the sampling.

FIG. 6 illustrates an antenna 60 suitable for treating coupled incidentand earth surface reflected acoustic waves in regions where the earthand/or mounted surface is flat on a scale large in comparison to awavelength. Again, use of thin structural elements 62 can make itunnecessary to determine the waves scattered by the antenna. Thecoupling of the incident and surface scattered waves introducesrelationships between components of the signal vector, reducing thedimensionality of the processing space and decreasing computationaldemand.

FIG. 7 illustrates an application of the present invention, whereinwhere small high density antennae, generally 70, can be deployed on avehicle 72. Shock, blast, and electromagnetic waves typically have shortwavelengths in comparison to vehicle dimensions, and higher frequenciescan be utilized. For a given natural local resolving power LRP, theantenna size can be reduced. A traceback program tracking back along raypropagation paths can be used to locate resolved sources of gunfire 74and shock waves, provided that contour map data is also supplied for theenvironment. Selected information can also be obtained for cell phones76 using electromagnetic antenna 78.

FIG. 8 illustrates deployments of the present invention where highdensity, high resolution antennae, generally 80, can be used with signalprocessing to help null out certain noise, such as noise from a vehicle82, as in removing vehicle-generated noise coming from the vehicle 82itself. Use of the noise metric and the associated mapping techniquewould allow tracking of sources of interest, particularly shock andblast waves, at wavelengths which are short in comparison with vehiclesize, even with significant vehicle noise. Small spherical andcylindrical high density arrays can be useful on relatively noisyvehicles. Traceback programs can also be employed for the location ofsources of projectile 84 firings, given contour map or triangulationdata. For lower acoustic frequencies, microphones and electromagnetictransducers can be placed along the body of the vehicle. In this casethe boundary conditions associated with scattering off the vehiclesurface should preferably be accounted for in the wave propagation modelused to construct the directional libraries, as is done with theelectromagnetic antennas shown in FIGS. 3A through 5B. The noise metricand associated adaptive mapping techniques can be employed to obtaintrue directions.

Other useful antenna system deployments can be made in accordance withthe present invention and can include severe storm 90 tracking withbuilding-mounted spherical acoustic and electromagnetic antennas,collectively generally 92, as depicted in FIG. 9 . Combined acoustic andelectromagnetic systems can provide range data for near simultaneouslyresolved thunder and lightning 94 bursts, while visitors can be trackedand monitored with acoustic arrays and traceback programs.

FIG. 10A depicts a towed, or, surface-suspended antenna array 100, andFIG. 10B depicts a bottom-mounted antenna array 102, with both beingconstructed in accordance with the present invention. Such a system canemploy hydrophones, thermistors, or magnetometers for detecting shipengines, internal waves of swimmer delivery vehicles, tsunamis, shippingtraffic, etc., depending upon antenna and wave scales. The towed antenna100 for side acoustic scan sonar applications of the types illustratedin FIGS. 5A and 5B, with electromagnetic transducers therein having beenreplaced by acoustic transducers, is illustrated in FIG. 10B. Such sidescan operations, using active pulses 104, can provide 3D views ofsubmerged objects, such as mine 106 on the bottom or a tethered mine108.

A spherically symmetric and/or “tree” antenna 110 based system,constructed in accordance with the present invention, for a harborsecurity monitoring is depicted in FIG. 11A, along with a cylindricalmonitoring array 112 as shown in FIG. 11B. The cylindrical antenna 112may serve as an acoustic or hydrodynamic wave antenna (surface,internal, etc.), and could monitor for self-propelled and/or swimmervehicles 114 as well.

Mountain deployment of an acoustic spherical antenna 120 is depicted inFIG. 12 , and such a deployment could be useful for remote traffic 122monitoring for situations where the terrain is not planar in theneighborhood of the antenna and where the antenna need not be mountedwith a particular orientation relative to the earth's surface. Atraceback program tracking back propagation paths can be used to locatesources of signals, such as from a sniper 124, emanating from themountain sides and/or other structures.

The wavelengths of interest and the nature of the propagating mediumplace restrictions on seismic wave antenna systems. Attenuation in theearth for interior waves is higher at higher frequencies, so lowfrequencies are generally more productive when making application towaves propagating through the earth. Embodiments such as those depictedin FIG. 13 might be employed in seismic exploration and/or facilitymonitoring. They can involve antennas, generally 130, with elementsburrowed into the earth's surface 134 with waves being generated usingan active mode, such as a bomb 136, as in FIG. 13 , or planar antennas140, 142, as depicted in FIG. 14 , for the detection of seismic surfacewaves, as detected by antenna 142, and for acoustic waves, as detectedby antenna 140. Geophones and/or magnetometers (not shown) can be usedas transducers for measuring fluctuations in seismic media or magneticinduced charges by metallic vehicles, respectively.

In simple seismic models, the wave equation modeling the physical wavecan be characterized by elastic moduli, and the waves are then bestdescribed by the P and S wave Hemholts decomposition (Lay and Wallace).In this case, both longitudinal and vector harmonics are needed. Use ofsmall bore holes 138 relative to wave dimensions of interest permitsignoring scattering by the illustrated seismic antenna structure, sothat, in one embodiment, only scattering of waves at the earth's surfaceshould preferably then be accounted for. A spherical antenna with anactive explosive source 136 would permit mapping of tunnel structuresand underground facilities, and multiple antennae would permit passivemonitoring and mapping of the facility.

FIG. 14 illustrates a combined acoustic, generally 140, and a seismicantenna array, generally 142, constructed in accordance with the presentinvention for measuring waves propagating 1 (in the neighborhood of thearray) along the earth's surface.

The antennae described above (with the exception of that of FIG. 13 )can typically be readily constructed and can provide for a minimalnumber of floating point operation, since the constant value of one ofthe coordinates of the coordinate system describes each transducersurface. Other antennae are possible, though, and could use a randomplacement of transducers, as might be done if the antenna must be placedremotely, such as, for example, in the scenario illustrated in FIG. 13if providing small bore holes were not possible. If transducers arerandomly placed (such as by air drop, use of projectiles, missiles, orthe like), software, and knowledge of their random positions through usof the global positioning system (GPS), could potentially allow a subsetof the transducers to be sampled via radio link, or some othercommunications method, for the purpose of defining signal vectors. Asubset of the transducers consistent with the Nyquist sampling criteriacould then be selected. In such an embodiment of the present invention,the thus formed randomly-shaped, or near arbitrarily-shaped, antennaecould also be used, but there would likely be a higher demand for signalprocessing power for certain types of selected information, such as withlocal wave field reconstruction. Calibration of such antennae could bedone in various ways, and could include the detonation of one or moreexplosive devices at a predetermined location(s) within the vicinity ofthe transducers and reviewing the outputs of the respective transducersin response thereto.

Note that with configurations of antenna constructed in accordance withthe present invention and meeting minimal Nyquist sampling requirements,such antennas can also be used in the sample and frequency domainswithout reference to partial wave expansions, particularly if onlydetection and tracking information is required.

The present invention also includes a self calibrating system, generally150, shown in FIG. 15 , which may include the self-calibrating systemcontained in FIG. 1 . Calibration of the system 150 corrects fordeviations from desired component tolerances and verifies that thesystem is operating within prescribed tolerances. The linear nature ofthe processing provides employment of simple techniques. Signal outputfrom D/A converters (not shown) driven by time series from an arrayprocessing unit AP drives a calibrating signal generator CSG inputting acommon signal to transducer elements. The complex amplification for eachchannel, generally A, for this signal can be determined, and deviationsfrom a standard (which can be one of the antenna transducers or areference signal) can be used as a basis for numerical correction ofinputs. This insures that the system channels effectively are identicalon each frequency over the bandpass. This procedure can be also be usedto check that voltage outputs, generally V, (and/or current) of eachchannel are within system tolerances. The process can be carried outautomatically each time the system is initiated or as desired by acontrolling operator. The system operator can also execute a manualcalibration and verification of system performance. Isolating impedanceor isolation devices, generally Z, assist in insuring that there islittle “cross-talk” between input calibration signals. Required phaseand amplitude corrections for each frequency can be incorporated intothe processing by modifying the matrix K from which the signal vector isobtained in the signal vector equation.

Operator calibration can be carried out if the operator is uncertainabout the functioning of internal calibrator. FIG. 16 is a singlechannel microphone signal driver, generally 160, for providing anacoustic pressure wave reference to a standard signal. The system can becalibrated one microphone channel at a time, and includes a microphone162, an acoustically isolating microphone receptacle 164 having apressure wave channel 166, and a driving earphone/speaker 168.

FIG. 17 is a schematic representation of calibration device, generally170, which can feed identical simultaneous signals to each channel. Itcan be used to determine simultaneously the relative complexamplification of each acoustic channel, again circumventing the need forelectronically matched signal components, and includes a microphone 172,a driving earphone/speaker 174, a symmetric acoustic wave channelizer176, and an acoustically isolating microphone receptacle 178. In thecalibration devices shown in FIGS. 16 and 17 , the acoustic signal feeddimensions should preferably be small in comparison to a wavelength.

FIG. 18 illustrates a composite seismic and acoustic system, generally180. Microphones 182 and/or geophones 184 can be simultaneously sampledas with two of the subsystems of the composite system 10 of FIG. 1 . Acomputer 186 is preferably used as an array processor. This embodimentis useful as a multimode detection and tracking device and for rangedetermination, since seismic and acoustic waves typically have differingpropagation speeds.

FIG. 19 illustrates a schematic representation of a method of thepresent invention for remote calibration of microphone positions, and isuseful when antenna dimensions are large making position calibrationdifficult. Using a field survey device 192 transducer locations on anantenna 190 can be verified can be verified or recalibrated when thepositions have been altered by environmental events.

The following example is provided for illustrative purposes, and it isto be understood that the present invention is not to be limited orconstrained by such example, as the present invention could be practicedin a variety of other applications and configurations.

EXAMPLE

In a representative example using the present invention, a deployment ofa simple embodiment of the present invention was carried out to validatethe capability for locating sources of blast and shock waves in amountainous environment using the signal averaging technique. In onetest 7 elements of a 16 element spherical array were employed as a 3Dantenna operating in reduced horizontal mode, after a field validationverified a partially broken data cable. The utilized signal vectorlibrary then consisted only of a subset of the 3D library correspondingto incoming waves near parallel to the earth's surface.

The array was deployed on one side of a bent canyon having canyon wallgrades running from zero to 60 degrees, with numerous rock outcroppings,protrusions, and canyon twists and turns. The width of the canyon rangedfrom approximately 150 to 300 ft in the vicinity of the array at thearray altitude, as viewed in different directions. Three shooterpositions were employed, all along a N-S line, the first being on theopposite canyon wall at 179 meters along a line nearly parallel to thecanyon's average axis, the remaining 2 were 32 meters north and 76meters south of the antenna Targets for the shooters were spread along aline on the opposite canyon wall, from south to west. All shooters hadroughly the same elevation as the antenna array. All of the consequentblast and shock wave time series were processed using the signalaveraging technique discussed above and appropriate for short durationsingle events.

A total of 39 rifle firings were observed. With the temporal processingwindow centered on the blast or shock wave pulse, only 5 rifle firingsresulted in error estimates of shooter positions above 5 degrees, withthe array having a resolving power of approximately 53 degrees. All ofthese 5 were associated with one shooter position, the one directlynorth of the array and out of line of site from the array itself. Thatposition was characterized by the shooter shooting from along anirregular rock wall ridge line, generating numerous echoes. The maximaerror observed in this instance was 14 degrees. The overall meanabsolute bearing error was 3.3 degrees, with 15 of 39 within 2 degrees.A movement of the temporal window to place the blast and shock wavepulses nearer to the end of the window to reduce the effect ofreverberation reduced the maximum error to 8 degrees, and 1 to 2 degreefluctuations in other bearings were noted, characterizing the accuracyof the process. With the new temporal window, the overall error wasnearer 3.5 degrees, with two thirds of the shootings associated witherrors of 3 degrees or less. Use of high density arrays of the typeproposed here is anticipated to greatly enhance accuracy.

Essentially identical processing results were obtained for the partialwave and Fourier signal vector representations. In all cases, dataprocessing involved 1 sec “snapshots” for data collection and 1 sec forprocessing. With use of an 18 element transducer array, the sameacoustic “pulse” processing technique was found to generate validresults inside buildings.

When using the reconstruction process for transmission of signals, asystem constructed in accordance with one preferred embodiment of thepresent invention operates as depicted in FIG. 20 . As discussed aboveregarding the signal reconstruction process, selected information mightinclude a set of analog modulation signals AI containing information tobe communicated to a number of receivers, generally R (FIGS. 24 through31 ). Each such signal is converted to a digital time series using ananalog to digital converter A/D, and the time series for each is passedas an input to the processor AP. The processor AP obtains the Fourierspectral components for each time series and selects the set of signalvectors needed for each from the signal vector library LIB of theprocessor AP, as specified by the desired direction for each signal tobe transmitted, as input from processor DI. The elements of the set ofthe signal vectors for each (with the specified frequency property) arethen weighted by the value of the spectral components of the givensignal. The weighted set is then inverse transformed to obtain the timeseries (as components) to be directed towards each individual transducerof the antenna, collectively XRs, of the system. The time series foreach of the signals so obtained to be transmitted to each transducer arethen added together, and the resulting time series are passed on to thedigital to analog converters D/As for generating the analog signals foreach transducer channel.

If the digital to analog converters D/As cannot reach the outputfrequencies required, an identical set of mixers, collectively Ms,driven by a common signal S can be used to raise the output to thedesired frequency band, since such a mixing process preserves therelative phases and amplitudes of the signals. The resulting set ofsignals can then be amplified, such signals referred to collectively as“AS”, and matched as required to drive transducers XRs to generate aphysical wave field PWF. Physical wave field PWF thus consists of thesuperposition of the physical wave fields carrying the selectedinformation to each of the resolved receivers.

It is to be noted that FIG. 20 is for illustration purposes only, and isto be understood that systems of the present invention can take onvarious other configurations as desired for the specific application.For example, the reporter RPTR of FIG. 1 could be represented by thesystem in FIG. 20 without using components AI and AD, and with thereconstructed time series of processor AP (FIG. 1 ) being used instead.

The sensor placement considerations for antennae operating in areceiving or passive mode also apply to the system's antennae when thesystem is operated in a transmission mode. The time series generatingsignals input into such an antenna provide for a mathematical model ofthe physical wave field in a neighborhood of the antenna, acting as“sample inputs.”

Knowledge of such sample inputs, or simply, “samples,” along withknowledge of the spatial derivatives along the signal surface, providesthe Fourier frequency components along at least one signal surface inthe neighborhood of the antenna containing the transducer elements. Thewave field's dispersion relation then provides knowledge of thederivatives away from such surface, thereby providing for determinationof the propagation away from the surface. In this sense, the spatial andtemporal Nyquist criteria play an important role in providing fieldpropagation.

The linear nature of a physical wave field to signal vector mathematicalmap in receiving mode enables signal enhancement through signal vectoraveraging, the attainment of relatively high resolving power through useof high element density arrays (and/or a consequent reduction innumerical processing demands), and for reconstruction of resolvedsignals. In transmission mode, the linear nature of the map also allowsthe reconstruction process to provide for the transmission of the signalobtained from the superposition of signal vectors, each being weightedby component spectral makeup of the desired signals. The Fouriertransforms of the resulting superposition components then provide thetime series to be directed to each system transducer.

Subject to power limitations and the reversibility of the transducersinvolved, for most cases of interest, the same antenna can be used forboth transmission and reception of selected information. However, in thecase of air acoustics and seismic physical wave fields, this may notalways be possible. In the electromagnetic applications, however,conductors and capacitors embedded into metallic surfaces may work ineither case, as can also be expected in the case of hydro acoustictransducer. The antennas of FIGS. 3, 4, and 5 could be used in thosecases. However, in the case of air acoustics, microphones may need to bereplaced by speakers to increase efficiency and transmission of acousticwaves.

FIG. 21 illustrates a planar array antenna, generally 200, operating in3D mode and capable of generating or receiving a signal inclined at anelevation angle EA and bearing B, provided its apparent wavelength inthe plane of the antenna is used to define the appropriate signal vectorlibrary elements. However, in this mode the resolving power of thesystem diminishes as the elevation angle increases

FIG. 22 illustrates a 3D antennae, generally 202, constructed fromplanar antennae sub arrays, generally 204, each sub array beingconfigured to operate with a modified dispersion relation so that thecomponent of the wavelength for each frequency (via the labeling ofappropriate signal vectors) is appropriate for the incident ortransmitted angle for an appropriate corresponding source or receiver.An expanded signal vector library LIB may be needed to handle themultiple incident component wavelengths involved. As a consequence,however, some resolving power may be lost since, as discussed above, thecomponent wavelengths have increased length.

Other possible antennae include a hemispherical antenna, generally 206,taking advantage of a planar reflecting surface (FIG. 23 ). In this casethe composite transmitted and reflected field has fewer degrees offreedom and therefore requires fewer transducers, but the signal vectorsshould be obtained from a wave field model incorporating the compositeincident and reflected waves off the planar reflecting surface. Thisantenna can operate either as a set of 2D subarrays or as a 3D antennabased upon a 3D signal vector library.

Some applications of the present invention are illustrated in FIGS. 24through 31 . These applications are intended to be example applicationsonly of the ability to simultaneously transmit signals in independentdirections on the same frequency band, and it is to be understood thatthe present invention is not limited to the applications shown in thefigures.

The ability to simultaneously transmit signals in independent directionson the same frequency band would provide for inter-airplanecommunication between airplanes (FIG. 24 ) within the same flight orgroup of airplanes, generally 210, such communication being with reducedthe risk of detection and reduced interference with other flights.

As shown in FIG. 25 , the present invention could also makecommunication on a network, generally 212, more secure by providing forreception and transmission more restricted in the locations and thedirections along which allowed network clients or participants,generally 214, are located. Additionally, the present invention couldprovide for increased signal density within specified bandwidths, byproviding a form of spatial filtering. One application could be thecellular phone industry, which could potentially find advantage andprofit from implementation of this present invention, since the systemof the present invention allows more cell phones to potentially beutilized within a give frequency channel.

Additional applications of systems constructed in accordance with thepresent invention are illustrated in FIGS. 26 through 31 . As shown inFIG. 26 , messages and/or other communications and/or portions thereofcould be transmitted to and from stations and/or teams of personnel,generally 218 in the field by a transmitter, generally 218A, where allcommunications could be simultaneously carried out on the same frequencychannel.

Or, as shown in FIG. 27 , messages and/or other communications could betransmitted to and from one or more ships, generally 222, fromsatellites, generally 224, generating signals simultaneously to and fromdifferent directions, reducing the time required for transmitting andreceiving signals and/or messages and signal interference.

FIGS. 28 and 29 illustrate applications of 3D receiving systemsconstructed in accordance with the present invention for bird trackingand/or bird watching. FIG. 28 illustrates a bird tracking apparatus,generally 226, implementing the systems of the present invention thatreports flocks of birds, particularly large birds, to an airport controltower, generally 228, or other aircraft monitoring location. Birds,generally 230, pose a threat to aircraft, particularly in flight pathsof such aircraft, and a 3D receiving system could provide warning offlocks of large birds, and in particular, vocal flocks in the vicinity.Multiple systems could provide range and bird flock location as well.

As shown in FIG. 29 , such 3D systems could appeal to bird watchersand/or lovers in their home or office, generally 232, for example,alerting them to the presence and direction of birds of interest 230 innearby trees or bushes 231, thus indicating where they are. The systemcould notify interested watchers by using its transmit mode withoutcausing appreciable interference to neighbors. Such systems can also bedeployed remotely to track migratory birds.

FIG. 30 shows a system constructed in accordance with the presentinvention having a wrap, generally 240, with transducers 242 of anantenna configuration, generally 244, used in a diagnostic applicationlistening for body sounds from within the human body 248.

FIG. 31 illustrates the application of the system in the cellular phoneindustry, appropriate simultaneous common channel directed communicationcould be made between resolvable cellular phone towers 250 andresolvable cellular phone users, generally 252, having antennas 254, thesize of which having been exaggerated for illustration purposes. Suchuse would increase band width participation and inhibit eavesdropping.It is to be understood, however, that although cellular phone users 252have been illustrated in cars, such is for illustration purposes only,and cellular phone users 252 could be in locations other than vehicles,buildings, etc. and can be indoors and/or outdoors.

FIG. 32 illustrates a system constructed in accordance with the presentinvention for monitoring traffic and/or vehicle movement. Acousticantenna 140 and seismic antenna 142, discussed above, measure acousticaland/or seismic waves propagating along the earth's surface generated byvehicle 262 traveling on road 264. Antennae 140, 142 are connected to areporter for transmitting information concerning terrestrial trafficand/or vehicle movement, such as speed, direction, vehicle type, thenumber of vehicles, etc. The outputs from antennae 140, 142 could beco-processed to improve the accuracy of the transmitted information,since antenna 140 receives sound-based information, and antennae 142receives seismic-based information concerning vehicle 262.

As such, the system of the present invention is capable ofsimultaneously transmitting and receiving spectrally competitive butresolvable signals using a single antenna and/or detector array.

The ability to simultaneously transmit and receive spectrallycompetitive signals to and from specific locations, possibly using asingle antenna for both transmission and reception, provides for spatialencryption for reception, transmission, and conveyance of signals.Although applications exist for the main types of physical wave fieldsdiscussed, i.e., electromagnetic, acoustic, seismic, and hydrodynamic,it is anticipated that one prominent application will be to thegeneration and reception of electromagnetic and acoustic waves usingantennae, which could be, but not limited to, the type described inFIGS. 2A-6 and FIGS. 21-23 employing transducers appropriate for eachwave type.

Spatially encrypted reception of a message involves a receiver generallysimultaneously receiving different portions of the message preferably onthe same frequency channel, receiving them from different resolvabledirections and re-assembling the message from these component parts. Thereceiver preferably consists of the present invention operating inreceiving mode, such as discussed above regarding FIG. 1 . The receiverreconstructs the signals belonging to the incoming directionscorresponding to each selected station, as per the above discussion onsignal reconstruction, and re-assembles the original message byinverting the procedure for de-composing the message into its componentparts.

FIG. 33A illustrates spatially encrypted reception for the case wherethere are two transmitters XCP1 and XCP2 generating physical waves PWCP1and PWCP2, respectively, conveying message component parts, or, messagecomponents. The two transmitted physical waves PWCP1 and PWCP2 aregenerally simultaneously sampled by receiver RCVR as part of a compositewave field including the two transmitted waves and background by areceiver RCVR compatible with spatial encryption. A receiver arrayprocessor AP could include a signal processor SP (or array processor)converting the samples, or, signal vectors, SV obtained from samplingthe incoming composite physical wave field into signal vectors SV1 andSV2 characterizing the physical wave fields of PWCP1 and PWCP2(associated with those incoming from given directions) and a messageassembler MA reconstructing from SV1 and SV2 the original message M.Alternately, the message assembler MA might reassemble a message fromits message component parts directly, in which the component partmessages are constructed directly from signal vectors SV1 and SV2 andthen merged into the complete message M. Whatever its type, the messageassembler MA preferably reconstructs the original message M using thedefinition for constructing the message component parts, with arrayprocessor AP being modified as required.

There are a number of possibilities by which component parts of messagesmight be defined. A text message might have different sequences ofletters from the message placed into different component parts, the rulefor decomposing the message into component parts depending upon howthose sequences are defined. The reconstruction of the messageincorporates this definition. Alternately, if an analog signal forconventional transmission of a message is provided, that signal might besampled and Fourier transformed to obtain the Fourier components of themessage. In this case, sub-sequences of the Fourier coefficients can beformed from the complete set and used to construct analog signalsdefining the component parts of the original analog signal message. Thereconstruction of the original analog signal obtained by the intendedreceiver sampling the physical wave field conveying the component partsobtains the set of Fourier coefficients for each component part. In thiscase the message assembler MA incorporates the definitions of how theFourier domain component parts were defined for each component part inorder to reconstruct the Fourier transforms of the original analogsignal and the message it carries as well as the respective times ofarrivals of the different component parts (the component part Fouriercoefficients generally need to be assembled into the set of Fouriercoefficients for the original message with the proper phases). Aninverse Fourier transform then allows the message assembler to outputthe original message.

There exists a multitude of possibilities for forming component parts ofmessages. Each message decomposition and reassembly procedure is basedupon the definition for each component part, and such definitionsconstitute an underlying form of encryption layered beneath the spatialencryption obtained from the general simultaneous transmission andreception of component parts into and from different directions,respectively, preferably on the same frequencies. Each message assemblerMA in each intended receiver typically incorporates such definitions,and such definitions could be distributed partially with each componentpart, so that receipt of all component parts would generally be requiredfor message assembly of only one part. The array processor AP for thereceiver in FIG. 33A should preferably correspond to a design consistentwith whatever component part definitions are employed.

The ability to carry out the message re-assembly operation depends uponthe location of receiver RCVR. Only in some localized neighborhood ofthe intended receiver RCVR will reception of all component parts alongproper direction be realized without difficulty, particularly if messagereconstruction also includes requirements on the arrival times of thecomponent parts, thus the characterization, “spatial encryption.”Transmissions of component parts by each station XCP1 and XCP2transmitting component parts to an intended receiver RCVR need to beconsistent with predetermined time of arrival requirements at thereceiving destination receiver RCVR. Other stations attempting messageinterception without sufficient resolving power would find messagereconstruction difficult, since message component part transmissionsoccupying the same frequency band would then interfere with one another.Receivers at locations other than that of the intended receiver RCVRwould not receive all portions with the proper timing or proper incomingdirections. The different component parts themselves could also beencrypted, with the merging process itself then requiring a furtherencryption key.

FIG. 33B illustrates an apparatus for the spatially encryptedtransmission of messages for the case where there are two intendedreceivers RCP1 and RCP2, the encryption capable transmitter XMTRpreferably being of the type depicted in FIG. 20 . In general, there canbe as many intended receivers as permitted by the resolving power of thetransmitter XMTR. One preferred embodiment of the present invention ofFIG. 33B involves the generally simultaneous transmission of messagecomponent parts transmitted as a physical wave PWF consisting of thesuperposition of two physical waves PWCP1 and PWCP2 conveying thecomponent parts to corresponding resolvable receivers RCP1 and RCP2. Thetransmitter XMTR consists of a message processor MP generating thesignal vectors SV1 and SV2 corresponding to the message component parts(decomposed from the message M) to be sent to the two receivers RCP1 andRCP2. The two signal vectors SV1 and SV2 are superimposed by summer Sinto composite signal vector CSV, which is converted by transmitter XPWinto a physical wave field PWF. At long range, the transmitted compositewave field PWF separates into its component parts PWCP1 and PWCP2, whichcarry the component part messages to the two selected correspondingreceivers RCP1 and RCP2. An interception of the original transmittedspatially encrypted signal in the near zone of the transmitter, wherethere is little or no directionality, would typically not produce anintelligible signal, while interception in the far zone would at mostgenerally yield only one component of the message, if the receivers RCP1and RCP1 are resolvable by the transmitting station XMTR.

The process of spatially encrypted transmission is generally a reversalof the corresponding process for spatially encrypted reception, and amodification of the process for the simultaneous transmission ofmultiple messages, preferably using a single antenna. The partialdirected transmissions received by each receiver RCP1 and RCP2 couldthen be assembled at a single location using predetermined componentpart definitions, or relayed to one or more spatially encryption capabletransmitters, as in the spatially encrypted conveyance of a message.

As shown in FIG. 34 , a spatially encrypted conveyance of a messageinvolving both spatially encrypted transmission through transmitter XMTRand reception through an intended receiver RCVR involves the linkages L1and L2 of selected intermediate receivers RCP1 and RCP2 used inspatially encrypted transmission to selected immediate transmitters suchas employed in spatially encrypted reception as discussed above. The solinked intermediate receivers RCP1 and RCP2 and transmitters XCP1 andXCP2 form an additional embodiment of the invention in which the signalvectors SV1 and SV2 obtained at the intermediate receivers RCP1 and RCP2are converted into signal vectors SVCP1R and SVCP2R driving theintermediate transmitters XCP1 and XCP2, which generate the physicalwave fields PWCP1 and PWCP2 conveying the component message parts to theintended receiver RCVR. The configuration in FIG. 34 thus links thespatially encrypted transmission and reception configurations of FIGS.33A and 33B. The signal vectors SVCP1R and SVCP1R are the output of thelinked receivers RCP1 and RCP2, obtained by replacing each directionallibrary signal vector that can be viewed as contributing to each of thereceived signal vectors of RCP1 and RCP2 by a corresponding directionallibrary signal vector corresponding to the direction from each linkedtransmitter XCP1 and XCP2 to the intended receiver RCVR.

Spatial encryption could involve layering standard encryptions formessage component parts under the spatial/merging encryption techniquesdiscussed above, with separate encryption keys required forre-assembling the component parts' messages, making interceptionde-ciphering virtually impossible, even if all component part signalsare received near the receiving station. Directional transmissions asallowed by this invention would also inhibit reception of message partsby receivers away from the intended receiver. If encryption anddecomposition/re-assembly keys were distributed inside the componentpart messages, it would not be necessary to provide the receiver withadvance knowledge of the incoming directions.

FIGS. 26 and 27 illustrate example scenarios where spatial encryptionmight be employed. In FIG. 26 , field operative personnel using thesignal reconstruction techniques of the invention could use spatialencryption for more secure communication with command posts at knownlocations (and also via satellites), while FIG. 27 illustrates ascenario for spatially encrypted communication between a ship at sea andsatellites, where command instructions could be conveyed in a moresecure manner. There exists a multitude of possible applications forsatellite transmission of spatially encrypted messages.

Another embodiment of the present invention allows for the determinationof information concerning a projectile. Under certain circumstances, asingle assembly or configuration (involving one location) of the presentinvention can be used to determine not only the direction but also therange to a source of a supersonic projectile, such as rifle fire, themiss distance of the trajectory from the observation point, and/or thespeed of the projectile, all without need of a second arrangement,assembly, or configuration of the invention, as would be needed fortriangulation. For range, such a determination requires the detectionand establishment of the directions of both the muzzle blast and shockwave generated by the projectile, the elapsed time between their timesof arrival, the ability to process associated data collected atfrequencies appropriate to each, and knowledge of the speed of sound.For the miss distance, such a determination also requires knowledge ofthe speed of the projectile, or equivalently, the miss distance for thepassage of a previous projectile from the same source. The processingprocedures required are those as described above for impulse type waves.In practice, such determinations require high accuracy and resolvingpower as allowed by the present invention.

FIG. 35 illustrates how range data can be inferred from measurements onthe muzzle blast and shock waves, while FIG. 36 illustrates a possibleapplication. Assuming a supersonic projectile is fired from some sourcelocation 270 and travels along the trajectory TJ, shock wave 276 movesout from the projectile in a cone making an angle ca with the trajectoryTJ. A receiver 272, which could be one as discussed above regardingacoustic signals in FIG. 1 , detects both the muzzle blast and shockwave at different times, the muzzle blast wavefront traveling a distanceR to the invention, while shock wave 276 has traveled a perpendiculardistance H from the source 270 at the time the shock wave passes overthe invention. The shock wave is assumed to propagate with the speed ofsound along the direction of H (line 280 in FIG. 35 ).

The invention is oriented such that the line 278 (FIG. 35 ) provides thezero direction off which the angle between the propagation direction ofthe shock wave 276 and the Ref is sa, while the angle between the Refand the direction of propagation R of the muzzle blast wave is ba. Sincethe shock wave propagates along H with the speed of sound c, and R isthe diagonal of the rectangle formed from the lines 280 and 282, is notdifficult to see that the rangeR=cdt/(1−cos(da)),where dt is the elapsed time between the arrivals of the shock andmuzzle blast waves at the location of receiver 272, and da=(sa−ba) andis the angle between the incoming directions of the shock and muzzleblast waves (between S and R in FIG. 36 ), where the counterclockwisedirection is here taken as positive (see FIG. 35 ). Note that it is notnecessary to know the velocity of the projectile to determine the rangeto the projectile's source.

The directions of the muzzle blast and shock waves can be determined asdescribed above in the discussion on the measurement of directions ofimpulse waves. The difference between the times of arrivals of the shockand blast waves can be determined once the directions for resolvableshock and blast waves have been determined. The corresponding signalvectors for each such wave can be used to determine a set of Fouriercoefficients for each. The latter can then used to construct theisolated signals of each such resolved pulse (as in signalreconstruction described above), so that differences in times of arrivalfor isolated paired blast and shock waves can inserted into the aboveequation. This reconstruction procedure provides for the determinationfor the time of arrival differences for multiple sources even if theshock or blast overlap in time, are spectrally competitive, or arehidden by other competing but resolvable signals, so long as theirpropagation directions are resolvable.

Also by referring to FIG. 35 , it can be seen that the miss distance MDcan be determined from trigonometry, and the triangle formed by thesides MD, R, and a portion of the trajectory TJ, i.e., line 274:MD=R cos(ca+da)=R*sin(Dda),where R is obtained as described above, and where Dda is the differencebetween the angle da for the observed projectile and a second angle da′(not shown) determined as da for the case of a trajectory making a veryclose approach to the antenna of receiver 272.

Equivalently, if cone angle ca is known, or if the speed of the type ofprojectile is known, then the angle da′ is known. For, in the lattercase if the projectile makes a close pass to the receiver 272, then thecomplement of the cone angle is very nearly equal to the angle da′.Furthermore, the measurement of the cone angle also provides knowledgeof the speed of projectile v, since the cone angle is related to thelatter bysin(ca)=c/v=cos(da).Knowledge of the speed of the projectile, the cone angle, or of a knownmiss distance can be used to determine from measured data a missdistance for a specific trajectory.

Note that the discussion here has been presented as if the speed ofshock wave propagation is independent of position along the shock wavefront. A more rigorous approach may involve local directions of theshock wave and its thickness through an analysis of the hydrodynamics ofshock wave propagation, but this simple approach could potentially givegood results.

The above considerations on range, miss distance, and projectile speedapply equally well when a three-dimensional embodiment of the inventionis employed, as the line R running from the source 270 to the receiver272 and projectile trajectory TJ typically define the plane shown inFIG. 35 . The above equations on these matters then are stillapplicable, with the angles da, Dda, and, da′ having the same meaning asgiven above. It is generally a simple matter to determine the angle dafrom known elevation and bearing angles measured for the muzzle blastand shock wave.

Applications of embodiments of the present invention to situationsinvolving both muzzle blast and projectile shock waves can address theproblem of determining the range and direction to snipers in counterterrorism efforts (FIGS. 7, 12 , and 36) using a single embodiment ofthe invention, as well as the range and direction to sources of highvelocity flat trajectory canon fire (FIG. 8 ), for example, as generatedby tanks and anti-tank weapons.

FIG. 36 illustrates the shock and blast waves passing over a vehiclepossessing one of the present embodiments. The angle da between thedirection of the normal vectors to the blast and shock waves R and S inFIG. 36 and the difference between their times of arrivals dt at thereceiver's antenna determines the range R. The present technique ofdetermining range using a single antenna has an advantage overtriangulation methods, since now communication between differentconfigurations of the invention is not required if both blast and shockwaves can be detected and properly processed. In the latter case, a lowprofile portable version of the type depicted in FIG. 36 would beparticularly applicable to infantry desiring to determine the directionand range of incident fire without infantrymen having to peek and lookfor sources of fire. Other appropriate embodiments can be employed atshooting ranges for the purpose of determining projectile speeds, sincesuch trajectories and consequent miss distances are readily available asinput, the latter being determined by placement of targets and shooterpositions at the range.

Another situation in which range to the source of a vehicle orprojectile and the miss distance to the vehicle's or projectilestrajectory can be determined is that which occurs when the vehicle orprojectile is continuously emitting physical waves, provided that thevehicle or projectile is moving near constant velocity. For the Dopplershift formula when differentiated with respect to time provides arelationship between miss distance, angular velocity of the bearingangle at the point of closest approach, and the Doppler frequency shiftof emissions as the vehicle passes. For then one knows the distance tothis CPA, the direction of the trajectory, and the distance to thesource if the emitted waves are tracked continuously from the vehicle'sor projectile's starting position two points sufficiently past the CPA.Applications of this technique include the tracking and sourcedetermination of RPG's and vehicles, such source determination being thelocation of the vehicles when tracking begins.

The fact that properly configured systems provide signal vectors thatenable mathematical and/or numerical models of the physical wave fieldin the neighborhood of the system's antenna implies, as discussed above,that the temporal and spatial derivatives for the physical wave fieldcan be obtained in this neighborhood. This means in turn that one ormore partial derivatives belonging to the physical wave field can beascertained in, on, or tangent to the surface on which antenna elementsare mounted, depending upon the neighborhood. These derivative fieldscan also be employed in detecting, tracking, and classifying sources ofthe physical wave field.

Interestingly, if the signal vectors (which can also be referred to asmodeling vectors) represent models of the physical wave fields, thedifferentiation of the physical wave field can be carried out using itssignal vector without actually constructing the physical wave fielditself. If the signal vector library is one of plane waves, orcombination of plane waves and waves reflected from the earth's surface,buildings, obstructions, or supports upon which the embodiments antennais mounted, then one or more partial derivatives can be used todetermine the direction of the wave's wave vector. Also, superpositionsof derivatives of partial waves decompositions can be used to testwhether combinations of partial waves characterizing sources actuallysuperimpose to represent the incoming wave field, that is whether or nota concluded collection of sources actually give rise to a physical wavefield of interest with associated propagation vectors.

The simplest example occurs if one tests to see whether the incomingphysical wave field is that of a plane wave incident on the antenna. Inthis case the component of the derivative tangent to a surface of anantenna should be consistent with the field model all along a surfacecontaining the transducers taking into account any boundary conditionsthat need be employed. The differentiation procedures can be employedwithout recourse to the detection and tracking techniques discussedabove, or can be used as supplementary procedures. In addition, it isclear that much information can be then obtained from the physical wavefield itself, without even recourse to a signal vector library. Thespecific approach depends upon how one characterizes the waves generatedby sources of interest.

A number of applications of the present invention involve surveillanceand security. FIGS. 9-13 and 28, 29, and 32 already address some ofthese applications. Other applications can include sonar and radarapplications as well as perimeter, work site, and littoral watersurveillance and monitoring.

FIG. 37 shows another embodiment of the present invention and includesan active acoustic arrangement, generally, mounted on a tower adjacentto a building, the embodiment emitting near spherically symmetric pulses286 propagating out from the transmitting antenna. A high resolutionreceiving antenna 285 receives reflections from the ground andsurrounding building, trees, and other environmental obstructions aspulse 286 propagates, with the receiver RCVR used to alert interestedparties of intruders 288 into the area. Incorporation ofbackground-induced noise into the noise metric (as discussed above)ensures that only deviations from the background are detected anddisplayed on a display screen (not shown). Multiple embodiments of thistype can be used to provide surveillance for extended structures,perimeter defense, and/or worksites. Passive embodiments, withouttransmission of a pulse, could monitor traffic in and around thevicinity of site.

FIG. 38 illustrates another embodiment of the present invention andincludes a second surveillance application, having an airport radar 289looking for deviations from ground clutter associated with backgroundbackscattering from hills surrounding the airport as caused by incomingor outgoing aircraft 290. By modifying the vector space as describedabove, distracting background scatter would not appear on the radarscreen 291. Note that this embodiment of the present invention mayeliminate sweeps across the radar screen used by conventional radarsystems. Only detections of deviations from the background and theirtracks, with possible dotted lines present on the radar screen 291indicating the positions of possible obstructions to flight, need appearon the screen 291.

FIG. 39 illustrates another embodiment of the present invention, andincludes an active littoral water surveillance system generating nearspherically symmetric pulses 294 resulting in reflections 295 from thebottom and reflections 297 from the water's surface, as might be used ina harbor or littoral region. A high resolution receiving systememploying a noise metric accounting for environmental backgroundbackscattering could detect and track deviations in the backgroundgenerated by intruders, such as by a submarine and/or remote controlledor swimmer delivery vehicle 296 moving in the area, and report suchevents to interested personnel using an appropriate reporter.

Additionally, the invention provides for determination of a projectile'strajectory, miss distance, and velocity using only one antenna array. Inone embodiment, these determinations incorporate a terrain model andknowledge of both the elevation and bearing angles for a directlyreceived shock wave, the associated shock wave reflected by the groundor other surface, the muzzle blast wave, and their times of arrival atthe antenna (not the times of arrival of each at individual transducerlocations as in TOA methods). In FIG. 40A, the trajectory T passes anantenna A and over a reflecting surface S. Direct shock wave D andreflected shock wave rays DR indicate the directions of the shock wavefronts as they move towards the antenna A. The dotted curve CR denotesthe instantaneous path of the refection on the surface S. The range tothe shooter (not shown) is assumed known as determined in the mannerdiscussed above. The shooter's range and the height H of the antennaabove the tangent plane to the points of reflection are also assumedknown, since a reflection model is provided for the propagation nearpoints of reflection.

Referring to FIG. 40B, the incident and reflected rays I and DR define aplane of approach for the reflected shock arrival. The ray D′, runningfrom the antenna to the trajectory, completes the triangle formed by DRand I. As an example of one possibility for obtaining the desiredselected information, the reflection model here considers that a shockwave reflection locally obeys the law of reflection. The angles betweenthe normal n to the tangent plane and DR, between the normal n′ and DR,and n′ and I are all equal, the angle a. Then using simple trigonometry,X and DR are obtained from H and angle a, and the complement angle (90minus angle a). Assume for the moment the angle b is known. Then D′ canbe calculated from knowledge of DR, the angle b, and the angle e, whichis (180 minus angle b minus (2× angle a)), and the law of sines. Thelength of I can also be determined from the law of sines. Since thedirection of D′ can also be determined from the above information, theequation for the trajectory T can be determined since now two pointsalong T are known, one being the endpoint of D′ and the other theposition of the shooter (which was determined above using time ofarrival information and the angle between the shock and “blast” wave).The miss distance is then known by determining the shortest distancefrom the antenna A to the now known trajectory T from the obtainedtrajectory equation. An initial guess for the angle b can be used, forexample, the polar angle difference (angle a minus angle d), also knownfrom measurement. Consistency between this result and the reflectionmodel defining the instantaneous position of the reflected shock on thesurface S provides validation of the result. That is, the instantaneouscurve of reflection CR is provided by the reflection model, given thenow determined trajectory and the direction and lengths of D′ and DR.Agreement between the direction of DR as implied by knowledge of thereflection curve CR and the output of the iteration technique validatesthe result and the value obtained for the angle b. Note that if theterrain is flat, then the results for DR and the time of arrival for thereflected shock wave also determine a range to the shooter in the samemanner discussed above, which can be checked against input to thecalculation, a further validation. Similar techniques can be used withmore complicated reflection models.

Additional embodiments of the invention involve exploitation of theability of the system to transmit and receive simultaneous spectrallycompetitive signals in the conveyance of multiple messages orcommunications, as indicated in FIGS. 24-31 and discussed above. In FIG.33A, the received message M carried by an incoming wave field (viewed inpart as a composite of fields PWCP1 and PWCP2 generated by resolvabletransmitters) can be considered as having independent messages orcommunications as component parts. Signal vectors of component fieldsfrom resolvable transmitters can be extracted from the composite fieldsamples as independent signal vectors, which in turn can be manipulatedto obtain selected information and/or signals to be directed toindependent parties. Such an application may be as illustrated in FIG.41A. In this case two transmitters XC1 and XC2 generate two independentcontributions PWC1 and PWC2 to the composite field at receiver RCVR,which is sampled to produce a signal vector SV. The receiver's processorSP converts the signal vector SV into signal vectors SV1 and SV2representing the contributions PWC1 and PWC2. It then manipulates theresults with a processor DM′ to construct the two communications C1 andC2 for the intended recipients.

For example, communications and messages can be interpreted as signalvectors, modulating signals, voice communications, video communications,text communications, signals derived from wave fields, digitalcommunications, and/or communications as carried by fields. The typedetermines the role of the processor DM′ in FIG. 41A.

Similarly, the message M of FIG. 33B can be viewed as the simultaneouslytransmitted composite message incorporating independent communicationsC1 and C1 simultaneously transmitted in the outgoing field PWF toresolvable receivers RC1 and RC2. As such, the system of FIG. 33B isgenerally transformed into a system which may be similar to that of FIG.41B, including a transmitter XMTR generally simultaneously transmittingspectrally competitive communications C1 to C1 to resolvable receiversRC1 and RC2. The communications C1 and C2 are prepared for transmissionby constructing two directed signal vectors SV1 and SV2 in a processorCP that are passed to a processor S which combines the to two signalvectors into a single signal vector CSV for simultaneous transmissionvia a composite physical wave field PWF, the latter generated by theconverter XPW. Thus, the component parts of message M of FIG. 33B cannow be viewed as independent communications to designated resolvablerecipients, as the physical wave field separates at large distances tothe fields PWC1 and PWC2 carrying communications signal vectors C1 andC2 to the resolvable receivers RC1 and RC2.

Another such embodiment is a relay station taking in possiblysimultaneous and spectrally competitive signals from a set oftransmitters on a common channel and rebroadcasting them over possiblyanother channel to resolvable receivers generally as a second compositefield. This embodiment involves coupling the output of FIG. 41A to theinput of FIG. 41B, such communications being in the form of messages asdiscussed above. Thus, FIGS. 41A and 41B together constitute a singlecomposite embodiment in which over some time interval an incomingcomposite wave field supplies input to a receiver RCVR, the receiveroutputs a corresponding signal vector SV, which in turn is converted bya processor S into two signal vectors C1 and C2 carrying the content ofresolvable transmissions XC1 and SC2. Signal vectors C1 and C2 are thenconverted into two transmitting signal vectors XSV1 and XSV2 whichdefine directed contributions to a composite transmitting physical wavefield on the same or possibly a different channel and which areconverted by a processor SVP into a composite signal vector CSVrepresenting this composite transmitting field. Finally, a converter XPWconverts CSV into the transmitting wave field carrying the content ofthe original transmissions XC1 and XC2 to resolvable receivers RC1 andRC2 on the same or other channel or channels. At long range thetransmitted physical wave field separates into the two transmittingfields carrying the content of XC1 and XC2 to resolvable receivers RC1and RC2. Thus, the message M of FIGS. 33A and 33B could be replaced byindependent communications, signals, or messages C1 and C2, as discussedabove.

FIG. 42 illustrates another potential embodiment of the presentinvention, namely, a setup for increasing spectral efficiency in acellular phone system. Several cellular towers are illustrated, each inpossible communication with another and with clients and on foot, inautomobiles, or other locations. As shown, clients in vehicles 296,envisioned as separated sufficiently in angle to be resolved by a signalantenna array on a tower, could be using the same frequency channels, asallowed by the spatial filtering and signal reconstruction enabled bythe present invention. However, the individuals and vehicles 298 mightnot be sufficiently separated in angle from other clients to beresolvable by the towers with which they are in communication, and theseclients could be bounced by the system to alternate channels ofcommunication so they would not in spectral competition with otherusers. Furthermore, the individual towers themselves might besufficiently separated in angle as seen by a satellite above, so thatthey could maintain spectrally competitive spatially filteredcommunications with the satellite overhead. In addition, towers could beexchanging such simultaneous spatially filtered spectrally competitivewave field communications with Mobile Telephone Switching Offices MTSOsshown in FIG. 42 .

There exist many possible applications of similar systems, for examplethe autos and individuals of FIG. 42 could be carrying pagers and/or“Blackberrys” and/or other PDAs, which would correspond to receivers,and in the latter case, transmitters of other communication systems. Inaddition, repeaters or relays could be set up for underwatercommunications between ships, divers, and submerged vehicles likesubmarines and swimmer delivery vehicles, as shown in FIGS. 11A and 11B,wherein, for example, a deployed buoy could receive electromagneticcommunications and/or messages from multiple sources and relay them viaacoustics to such entities. Other applications include the Amateur RadioService, which uses repeaters on many of the higher frequency bands. Infact, any entity which executes communications to be directed toindependent recipients using resolvable receivers could potentiallyprofit from increased spectral and/or temporal efficiency inbroadcasting and receiving messages.

Similar applications arise in directed inter aircraft communications asalready illustrated in FIG. 24 , or between formations or in subsurfaceacoustic communications between divers, submarines, or other submergedentities. For example, in FIG. 24 one could imagine the formation ofplanes as a formation of submerged vehicles in acoustic spectrallycompetitive and/or spatially filtered communication, or the tower ofFIG. 31 effecting electromagnetic communications with multiple clients(police, firefighters, emergency personnel, commercial applications,etc.).

The wave nature of the communications permits application of the presentinvention to several different physical wave types; only the structure,transducer type and configuration, and/or processing electronics ofantenna/receiver systems need possibly be changed. The concept andprinciples of operation are not changed. Thus, with the presentembodiment one has the possibility of employing a new “multiplex”communications technology, possibly utilizing spatially filtering activeantenna systems, such that temporal and spectral efficiency is increasedbeyond current duplex methodology, with other types of capacityincreasing the methodologies potentially being layered beneath, such as,for example, code division multiple access (CDMA), time divisionmultiple access (TDMA), global system for mobile communications (GSM)systems, etc.

The ability to provide range, tracking, and direction data as alreadydescribed on multiple resolved objects of interest has a number ofapplications. Such selected information provides for aiming a goodnumber of devices, such as cameras, telescopes or field glasses, lasers,and weapons of various types. Indeed, such selected information obtainedfrom the here described systems having high resolving power can be inputto existing pan and tilt mounting system controllers. The motion of evenmultiple objects and vehicles with identical wave emissions can then besimultaneously followed and predicted (tracking implies knowledge ofvelocity) for photographic, surveillance/alarm, and other applications.For example, scenarios of this type can be read from FIGS. 8-14, 12, 27,31-32, 36-37, and 42 , scenarios in which multiple wave types areinvolved, but for which the methodology is the same when applied tohardware appropriate for the physical wave type involved. In addition,active systems, involving ranging, direction and tracking data obtainedfrom reflections from transmitted waves, can be used for steeringrobotic vehicles, without the need for having antennas that rotate

The determination of Nyquist compliant signal vectors obtained fromsignals of properly spatially configured transducers (a la Nyquistsampling criteria) provides for the determination of the coefficientsdefining mathematical partial wave expansion models for the fieldsinvolved, regardless of the type of field. For example, with theSpherical Harmonic partial wave expansion, one can determine theexpansion coefficients for the expansion's contributing terms for anincoming physical wave field by taking scalar products between samplesof the physical wave field or its spectral components and the partialwave functions. Knowledge of the contributions for known waves ofinterest then provides for the determination of selected informationdirectly from the field modeling functions involved, using thesuperposition principle and known expressions for a single source'sexpansion coefficients as known functions of the directional coordinatesto the source (for example, see Jackson, Classical Electrodynamics,1962, Chapter 16, p. 567, eq 16.127), from which one or more sourcedirections can be determined. This approach eliminates the need for asignal vector library, greatly reduces the number of needed scalarproducts, and consequently greatly reduces the required number offloating point operations (FLOPS) greatly increasing processorefficiency.

Use of integral solutions to the physical wave fields provides fornumerical models of solutions away from a physical wave surface usingthe already mentioned Khirkoff type surface integral representations andintegral solutions which can be obtained from solutions used inuniqueness proofs associated with initial conditions (See Jackson,Classical Electrodynamics, 1962). Selected information can then beobtained directly using mathematical models defining the incoming wavefields. The techniques described above provide for receivers,transmitters, and transceivers operating with spatial filteringcapability. Such systems are able to address communications fromsimultaneous signals without the need for antenna rotation, providedsuch signals are resolvable.

In one implementation of the present disclosure, a spatial filteringcapable receiving communications system needs to generate or haveknowledge of source directions, an antenna structure having transducerscompatible with spatial and temporal Nyquist requirements and ofoutputting signals representative of sensed field components attransducer locations, and one or more processors capable of implementingmathematical field models representing both possible incoming sourcewave contributions at the antenna and required components of thereceived field. Processor(s) then use these models to convert antennaoutput signals into communication signals output to a human or device.The method for a spherical highly conducting metallic antenna structureis outlined here as an example. This outline utilizes the fielddetermination approach of Jackson's text (See Jackson, ClassicalElectrodynamics, 1962), incorporated here by reference, with equationscited below being from that text.

Angular partial wave functions needed include vector spherical harmonicsx_(lm)(θ,φ) as functions of angular coordinates of positions in space.Such angular vector harmonic functions are constructed from the ordinaryspherical harmonics Y_(lm)(θ, φ), see eqs. 16.25 to 26 and 16.45, andform the basis for constructing a complete orthogonal set of vectorfunctions as demonstrated in 16.132.

The total electromagnetic field models for a field component ofwavenumber k in a neighborhood of a perfectly conducting sphericalmetallic structure consists of a PWE in the x_(lm)(θ, φ) based sethaving expansion coefficients containing as factors the sphericalharmonic Y_(lm)(θ_(s), φ_(s)), where (θ_(s), φ_(s)) specifies theincoming direction from the source s, spherical Bessel functions ofwavenumber k and the structure's radius of order 1, and incoming waveamplitude components A_(s)(k) for each source, the latter also afunction of wave number. The total solution consists of a superpositionof solutions for all sources and their contributing wave numbers.

Jackson's text provides the complete solution for the sphericalstructure (incoming eq. 16.139 plus scattered wave eq. 16.141) for anincoming wave incident along the polar axis direction, meaning a vectorpartial wave expansion satisfying electromagnetic boundary conditions atthe surface of the sphere. Solutions are provided for bothpolarizations. The desired solutions for an arbitrary incoming incidentdirection and polarization is easily obtained from Jackson's usingelectromagnetic field models for E and B in eqs. 16.133 and 16.134constructed from eq. 16. 127 rather than eq. 16.129, i.e., E and Bfields based upon exp(ik*r) instead of exp(ikz), where k is thewavevector and r the radius vector. This allows determination of themodel for incident plus scattered fields at the surface of the‘spherical antenna structure’ for arbitrary source directions specifiedby angular coordinates (θ₅, φ_(s)), models which insure satisfaction ofboundary conditions for the field in a neighborhood of a good conductor.Note that the E and B contributions from each wavenumber are obtainedfrom eq. 16.127 using eqs. 16.42 and 16.44.

The spherical structure's complete field model's lm^(th) expansioncoefficient's functional dependence for an incident wave having anarbitrary incident direction involve known scattering phase shiftfunctions as well as the factors mentioned above, but the factorT_(lm)(θ_(s), φ_(s)) is still present and unaltered. For simultaneousmultiple contributing sources one can take the superposition of suchscattering solution models to model the incoming field at the antennastructure, the corresponding weighting coefficients A_(s)(k) containingthe communications to be determined.

One method of obtaining directions and communications uses the signalsoutput from the structure's transducers and a processor to relate thesesignals to the incoming E and B field model components (via boundaryconditions) at the transducer locations. The total incoming wave model'sexpansion coefficients can be found by taking scalar products betweenthese E and B field components and the orthogonal vector harmonic setevaluated at the transducer locations, and manipulating thesecoefficients and known expressions for the Y_(lm)(ϵ_(s), φ_(s)) toobtain both the directions (θ_(s), φ_(s)) and the A_(s)(k) containingthe s source's communication. The A_(s)(k) can then be Fouriertransformed to obtain the communications from each resolvable source.

The processor can also execute scalar products between the incomingfield and suitable test source models (E and B PWE models evaluated atthe structure's transducer locations, obtained via eq. 16.127 satisfyingboundary conditions for an incoming wave from a specific direction, andweighted with wave number amplitudes B_(s′)(k)). The scalar productdefines a test function of the angular direction of the test source. Theincoming field model can be viewed as a superposition of test sourcemodels obtained from normalizing test source partial wave expansions.For resolvable sources the test function has maxima at the direction ofa contributing resolvable source with sufficient signal to noise ratio.Inputting obtained directions and with proper choice for the testsource's expansion coefficient B_(s′)(k) the test function providesdetermination of the source's signal amplitudes A_(s)(k).

For example, for the scalar acoustic field the test function has theform Σ_(sl)A_(s)(k)P_(l)(cos(γ_(ss)′)) when transducers (microphones)and nearby structures are small compared to a wavelength, where s and s′refer to a contributing source and the test source, respectively, andγ_(ss)′ is the angle between them. The sum is over sources s to theincoming field and the expansion index l. Since P_(l)(1)=1, the functionhas near maxima when γ_(ss)′ is zero, when the angle between the sourcedirection and the test source's direction vanishes. Knowledge of thedirection to the source's direction then permits determination of thesignal amplitudes A_(s)(k).

The directions and amplitudes of remaining probable resolvable sourcescontributing to the incoming field component with wavenumber k are foundby subtracting the field for the s^(th) source (weighted with its abovedetermined amplitude from that of the incoming field components atsensor locations), and proceeding as with the original test function tofind the wave amplitude and direction of the next source. The process isrepeated until criteria for detection and source classification are nolonger met, until one is left only with background “noise”.

Test functions also provide for definitions of detection andclassification for use in processing. Once a “background” test functionhas been determined with all probable sources removed one can considerthe background with only one of the probable sources included, anddetermine the consistency with the result with a test function obtainedfrom one of the probable sources alone. Then can determine if thesuspected source's determined amplitude and shape are compatible withthat expected for a test function resulting from a single source alonewithin a given background of signals. This procedure allows both fordetection and classification of a signal as an isolated source. Notethat all scalar products involved need involve summing only over sensorpositions since the spatial Nyquist criteria has been observed.

In one implementation of the present disclosure, a horizontal ringspatial filtering receiving system is treated as receiving incomingwaves propagating near horizontally is illustrated in FIG. 43A-C. Forthis receiving system the vector wave expansions can be viewed as anorthogonal cylindrical function expansion in the azimuthal angle φ.Nyquist criteria for transducer placement and sampling rate areobserved. The process for obtaining communications from resolvablesources is generally procedurally the same as that outlined, but withthe switch to angular cylindrical harmonic functions of φ.

The partial wave expansion for the ring array is obtained from thespherical wave expansion by setting the polar angle therein to near 90degrees, appropriate for incident waves propagating near parallel to thehorizontal plane. The ring contains transducers consisting of sensorelements 299 mounted on its circumference 300, with each such elementcoupled to the transducer's electronics 301 within a protective housing302, the transducers generating signals from currents and/or chargedensities sensed along the ring. The transducer coupling to the ring maybe inductive or capacitive as, for example, depicted in FIG. 3B forcapacitive coupling and FIG. 4C showing a segment of a toroid 46 withthe ring passing through the toroidal center for inductive coupling. Thetransducer electronics 301 may include filters, amplifiers, and mixersas, for example, in the front ends of software defined radios, and/orsoftware defined radios.

Models for the transducers relate the charges and currents sensed to thenormal E and tangential B fields at the rings surface, the transduceroutputs designed to characterize the field. All transducer share acommon local oscillator 303, signals for each obtained through use of aduplicator 304 faithfully reproducing the phase and amplitude of signalsof the local oscillator 303. Each transducer set (299 and 301) outputs Iand Q signals (as with software defined radio front ends) to dataacquisition card inputs of an acquisition card located within orconnected to a processing, control and display unit, generally 305,having one or more processors. The acquisition card passes the digitizeddata to the processor(s) in 305 for implementing models and operations,which in turn outputs signals of resolvable sources as information forhumans or devices, which can display or accept selected information suchas source directions and communication content.

Low frequency signals from transducers insure very little loss alongtransmission lines 306 descending down the antenna support mast 307 to aprocessor (not shown). Alternately, Wi-Fi or fiber optic cable can beused to transfer DAQ outputs from the housing 302 to theprocessing-display unit 305 with little loss and with greatly reducedbandwidth.

Placement of the system's electronics in the antenna, except for thetransducers, is not critical and can be chosen to fit antenna physicalstability and communication electronics efficiency. For example, thesoftware defined receiver front ends can be place at transducerlocations and processing could occur within the mast mounted hardwarehousing, with only control and display units at ground level or someother location.

A block diagram characterizing one possible implementation of a spatialfiltering receiver is illustrated in FIG. 44A. Therein transducers XDCRsense an incoming wave field (IWF) output down converted signals to aprocessor MP, signals representing the E and B field components attransducer locations. MP digitizes the signals s_(i)(t) of eachtransducer and maps those via scalar products (taken over transducerlocations) with test model source functions into a test function. Thelatter is passed to an extraction processer EP to obtain sourcedirections either from user input or from the test function, and thenuses these source directions to obtain the coefficients A_(s)(k) for anincoming source wave field model. The extraction processor EP thenobtains the communications from the A_(s)(k) via Fourier transform fromthe source directions and their signals are then forwarded to humansand/or to a device for extracting information from the transmittedsignals. Note that the Fourier coefficients A_(s)(k) and A_(s)(k) forthe original and down converted signals are the same for thecommunicated information.

In another implementation of the present disclosure, spatially filteredtransmission is realized by constructing systems operating essentiallyas the above described receiver operating in reverse, as FIG. 45Billustrates. A source card supplies low frequency signals A_(r)(t)containing information to be communicated to a number of receivers(indexed by r) along with the directions (θ_(r), φ_(r)) for propagationto these receivers. Then using the input directions and a correspondingtransmitting PWE model for a transmitted field (outgoing waves only andmeeting boundary conditions) for each direction, the processor CP firstconstructs time series (indexed by i) for each direction s_(rj)(t_(i))for each transducer channel (indexed by j), sums the resultant timeseries sets to form the s_(j)(t_(i)) for the total field in theprocessor TFP. Processor TFP then uses a simultaneous multichanneldigital to analog converter to provide signals s_(j)(t_(i)) fortransducers XDCR. The transducers XDCR then upconvert these signalsusing a common local oscillator signal to convert the s_(j)(t_(i)) forthe total field TWF into an outgoing set of signals driving the antennaat transducer locations, where the XDCR may also include matched signalamplification.

In some cases and situations, the example implementations can beenhanced by adding a sector selector to the system for receivingcommunications. The role of the sector selector is to reduce thedimensions (size) of the vector spaces and table lookups involved insubsequent processing (thus reducing the number of FLOPs) by restrictingconsiderations to a subset of possible incoming directions. Such animplementation may incorporate the same system of FIG. 43 , but whosecomponents are suitable modified to accommodate a sector selector. Thesector selector uses the signals and/or data from individualtransducer/receiver pairs to define detection, where one or more pairsare chosen as best meeting detection criteria. Further processing thenutilizes data from all pairs, but operates under the assumption that theincoming signal is incident in the one or more sectors defined by thecorresponding “beam pattern(s)” or amplitude function(s). This allowsthe limiting of subsequent data processing to the ‘effective’ angularbeam pattern sector (incoming aperture) associated with the chosen oneor more pairs generating the detection. There are several possibleimplementations of a sector selector.

For example, in one implementation, the ‘detecting pair’ could be thatgenerating the signal meeting amplitude requirements above some desiredthreshold at the processor 305. With detection criteria met, theprocessor 305 then triggers data collection storage for all pairsassociated with an event, so that subsequent data processing forselected information takes place as described previously above inconnection to with the embodiment but with processing restricted topossible incoming angles defining directions within the correspondingchosen effective angular aperture.

Turning to FIGS. 43A, B, and C in one nonlimiting implementation, theselector can be incorporated into a stand-alone system within aprotective housing 302. The system scans each pair's output and with theapplication of preselected detection criteria then sends a triggeringsignal and the detecting pair's identity down the transmission line 306(and/or wirelessly) for use by the processor 305, which is continuouslycollecting pair outputs; however the processor 305 need not processunless a trigger is received indicating a threshold is reached. Such aprocess provides a more enhanced embodiment particularly for threedimensional arrays, where overall processing speed and requiredprocessing efficiency are considerably enhanced. For electromagneticsystems the process of the present disclosure is most easily implementedif the antenna is symmetrical (as with a ring or sphere) with respect tointerchange of pairs, as then all impedances are uniformly matched.However, it is understood that the system and process of the presentdisclosure is not limited to symmetrical antennae and could be used onasymmetric antennae, if desired.

Alternately, it should be noted that one could also utilize the sectorselector as a basis for a stand-alone system, as in FIG. 45B, wheneverpinpoint directionality is not needed and/or processing capabilities arelimited. Here a switching system mounted in the housing 302 moves thereceiving or transmitting beam pattern from one direction to another byswitching in and out transducers, using a single transmission line(and/or wirelessly) for switching signals/instructions and transduceroutput communications (by passing such information along a transmissionline (and/or wirelessly) using a different bandpass than that of thecollected data or received signal switching and bandpass techniques asfor example described in the ARRL Handbook, 2016). The detection cantake place in the stand-alone system and the sector output choice can bepassed to an embodiment's processor 305 as described above via areporter; or, the sector selector can simply used for normalcommunication purposes for receiving and transmitting communications.Such a system is illustrated in FIG. 45B. Note that the reporter can beeither a link to a main processor 305 completing the previousembodiments processing or a receiver and/or transmitter for transmissionto a particular sector.

One example of a tranducer, shown in FIG. 45C, illustrates a crosssection view containing in part the metallic radiating or receivingelement 308 of FIG. 45A passing through the toroid of a transducer. ring308 of FIG. 45A. The transducer 309 matches the impedance of thetransmission line to the radiation resistance of the antenna of thestand-alone system, and consists of a toroid 314 supporting a coil 315that is connected to a switch 317 and variable capacitor 316, which inturn is connected to a coax transmission line 318. The capacitor 316 andthe inductor combination so mounted constitute a tuned circuit for wideband matching of radiation resistance to transmission line impedance.The active transducer is selected by a switching system 310 closing theswitch 317 to connect it to the transmission line 318 running down themast 311 and connecting the received signal to a processor ortraditional receiver 313 as in FIG. 45B. Use of the Nyquist criteria fortransducer placement establishes the resolving power of the sectorselector and thus indicates the region of coverage or sector that can beattributed to the chosen transducer. Thus the ‘selecter’ can alsofunction in a stand alone communication system whose endpoint is areceiver, transmitter, or transceiver, depending on whether signals aresent up or down the transmission line and/or wirelessly, with fortransmission all signal directions being reversed.

Note other suitable transducer/impedance matching systems are describedin various editions of the ARRL Handbooks (included by reference) overthe years, but are not presented here for the sake of brevity. Theseinclude matching couplings between transmission lines and the antennastructure using capacitive coupling for high impedance loading, use oftransformers, and including parallel as well as series tuned circuits.

It should be pointed out that the sector selection embodiments describedhere can be further enhanced through addition of parasitic elements suchas concentric metallic parasitic rings to further enhance beam patternsassociated with the antenna structures, provided Nyquist criteria iscomplied with in the designs.

Another implementation of the present invention includes a receivingsystem (FIG. 46A) wherein a structure STR is placed within a mediumsupporting propagating wave fields. The structure incorporates sensors Xconfigured to sample charge and current density fluctuations F withinthe structure, the fluctuations being produced by a physical wave fieldpropagating in the medium. The sampling occurs in such a way that thesefluctuations F can be determined substantially everywhere within thestructure from the samples obtained from the structure output signals.An interface IF passes on incoming wave content to a human or device.

The structure can be a solid, a shell containing a gas, or a containedliquid, or a combination thereof. The incoming field waves IWF generatefluctuations F within the structure and a scattered wave field SWFpropagating outward from the structure.

Solutions to the structure scattering problem are used to define a mapproviding a correspondence between incoming wave field directions andconsequent resulting fluctuations within the structure, and thus to thecorresponding consequent structure's multichannel output signals s(t) (iindexing the transducers) and/or their samples. This process defines adirectional model. Appropriate directional models have been discussedpreviously in this specification and one can use signal vectortechniques, including use of partial wave expansions whose coefficientscontain the angular coordinates for the source of an incoming wave.

The directional model used with a detection threshold provides for thedefinition of a set of collections for each sensor, each collectionbeing a connected set of directions detectable above some threshold. Thecollections of a single sensor define a sector. Each collection within asector is assigned a weight providing a relative amplitude within thatsector characterizing how a signal direction will be contained within aparticular collection, the weights reflecting the relative amplitude andphase of each collection. The sensors should be configured so that thetotality of their collections cover the possible incoming wavedirections of interest. Note that each sensor within the structure neednot have an intrinsic individual beam pattern as it is the structureproperties that define the internal fluctuations. The structure is notan array of transducers each with its own intrinsic beam pattern.

There are three ways in which the system of FIG. 46A can be implemented.The simplest is to use the processor RP to select the sector with thestrongest signal output. Each such sensor then can be viewed asassociated with a different structure amplitude response pattern, thosepatterns stored in a library L. At the other extreme, the directionalmodel alone can be used to infer the directions of possible sources, Lnow containing the map and allowing the processor P to access this map.This follows the path of the previous procedures outlined above. But useof the directional model as a stand alone method requires moreprocessing (i.e. more FLOPS) and thus more energy and power. A thirdpossibility is to utilize the sector and directional models together toreduce the processing required when a large number of sensors areinvolved. The sector model collections and their respective weights anda detection criteria can be used to reduce the needed dimension of thevector space of the directional model by restricting possible incomingdirections to those of identified collections. This reduces processingenergy requirements and time. The signal content carried by the incomingwaves is then passed through the interface IF to a human or device.

As a non limiting implementation, the structure STR is metallic and thecurrent and charge densities are the electric current and chargedensities within the structure. Typically in this implementationfluctuations F generated within the structure are confined to within askin depth of the surface, within a thin layer adjacent to the surface.The sensors can be inductors and capacitors as previously discussed.With proper placement and design of these capacitors and inductors assensors, the sensors respond substantially only to surface charge andcurrent density fluctuations nearly confined to within a skin depth andtheir “sector” patterns are considered those of the structure at thatlocation. The ring antenna of FIG. 43A is such a system with itspossible capacitive and inductive transducers as discussed previously.

In another implementation, the current and charge densities fluctuationsare mass current and mass density fluctuations (or deformationfluctuations) as would be generated in a body by acoustic or seismicfields propagating in a medium, such as a liquid or solid, exterior tothe structure. The structure interior could be air, water or solid, orsome combination thereof as needed to obtain a desired wave response(possibly as resonant wavelengths) within the structure. Sensors mayinclude microphones, piezoelectric crystals, interferometers,hydrophones, etc., or whatever is appropriate for the makeup of thestructure and the nature of the internal fluctuations. In each casehowever, modeling connects the structures interior fluctuations to thoseof the exterior medium by ensuring the proper boundary conditions (in afield model) are satisfied at the structure's surface. One can usepartial wave functions, Green's functions, and other well knowntechniques to model the fluctuations and fields involved.

In an additional implementation, referring to FIG. 46B, one can use themultichannel transducer structure STR to transmit simultaneouscommunications to intended receivers via an outgoing propagating wavefield XWF. There are two most prominent possibilities. Most simply, onecan select the sector having a collection containing the direction ofeach intended receiver and transmit using the transducer for thatsector. For simultaneous multi receiver communication, using thesuperposition principle, one uses the library L containing thecorrespondence between outgoing field propagation directions and thesignal sets to be input to the processor TP. One then uses the processorTP to take a superposition of the multichannel signal sets needed to forsuch receiver communication to generate the needed current and chargedensity fluctuations F within the structure. The external interface IFprovides the signal containing the communication, which is then taken byTP to modulate the composite signal set sent to the structure. Requiringsatisfaction of boundary conditions (outgoing waves only from thestructure) in the modeling for the field insures that the charge andcurrent densities within the structure generate the proper fields in theexternal medium needed to propagate the communications to the intendedreceivers. Finally, one can combine the transmit and receive operationsinto a single unit by incorporating the processors TP and RP into asingle unit.

In another implementation of the present disclosure, a method isprovided for determining directions to and outputting communicationsfrom at least one source contributing to a source wave field in apropagating medium. The method includes providing a structure placedwithin the propagating medium, the structure incorporating multipletransducers whose output channels output simultaneous signals consistentwith temporal and spatial Nyquist criteria that represent andcharacterize fluctuating charge and current densities within thestructure. The method includes providing a directional model defining amap between the direction to each possible source in the propagationmedium and a set of output signals created by the fluctuating charge andcurrent densities generated by the waves emanating from each possiblesource in the propagation medium, and further includes providingdetection criteria for determining the presence of signals from at leastone source in the propagation medium in each output channel.Additionally, the method includes providing a sector model constructedfrom the directional model and detection criteria, the sector modeldefining collections of possible source directions and collectionweights for each output channel, and also, providing a processorcommunicatively coupled to the signals from the output channels andconfigured for analyzing their signals. The method further comprisesusing the processor, the signals from the output channels, the detectioncriteria, and the sector models collections and weights to identifyprobable collections of directions possibly containing the at least onesource in the propagation medium and/or outputting the communicationsfrom the at least one source.

Additional implementations of methods of the present disclosure mayinclude the antenna structure including parasitic elements and/or beingmetallic and the charge and current densities being electric current andcharge densities, respectively, and/or the antenna structure being ofmetallic material and the charge and current densities are mass currentand density fluctuations, respectively.

Moreover, implementations of methods of the present disclosure mayinclude restricting consideration of incoming directions to thosecontained in the identified possible collections of directions and usingthe processor, signals from the output channels, the directional model,and the identified collections of probable directions to determine thedirections to and communications from at least one source, to therebyreduce the time and processing required to obtain the selectedinformation.

Further implementations of the present disclosure may include a systemfor determining directions to and outputting communications from atleast one source contributing to a source wave field in a propagationmedium. The system includes a structure placed within the propagatingmedium, the structure incorporating multiple transducers whose outputchannels output simultaneous signals consistent with temporal andspatial Nyquist criteria that represent and characterize fluctuatingcharge and current densities within the structure. A directional modelis provided defining a map between the direction to each possible sourcein the propagation medium and the set of output signals created by thefluctuating charge and current densities generated by the wavesemanating from each possible source. Detection criteria is provided fordetermining the presence of signals from at least one source in thepropagation medium in each output channel, and a sector model isconstructed from the directional model and detection criteria, thesector model defining collections of possible source directions andcollection weights for each output channel. Additionally, a processor iscommunicatively coupled to the signals from the output channels andconfigured to use the signals from the output channels, the detectioncriteria, and the sector model collections and weights to identify andoutput probable collections of directions possibly containing the atleast one source in the propagation medium and/or outputting thecommunications from the at least one source.

Implementations of the present disclosure may include a system where theantenna structure is metallic and the charge and current densities areelectric current and charge densities, respectively, and/or where theantenna structure includes parasitic elements and/or is metallicmaterial and the charge and current densities are mass current anddensity fluctuations, respectively. Additionally, the processor may beconfigured to restrict consideration of possible directions to those ofthe identified collections of possible directions, signals from theoutput channels, and the directional model to determine the directionsto and communications from at least one source, to thereby reducerequired processing time and system energy requirements.

In another implementation of the present disclosure, a method isprovided for outputting communications to at least one receiver via aphysical wave field in a propagation medium, where the method includesproviding the directions to the at least one receiver and providing astructure placed within the propagating medium, the structureincorporating multiple transducers generating consistent with temporaland spatial Nyquist criteria fluctuating charge and current densitieswithin the structure from the transducer input signals. The methodfurther includes providing a directional model relating input signalsets to the propagation directions of consequent fields generated bysaid fluctuating charge and current densities within the structure andproviding a sector model constructed from the directional model, thesector model defining collections of possible receiver directions andcollection weights for each channel. Additionally, the method includesproviding a processor communicatively coupled to the structure's channelinputs and configured for generating their signal, and using theprocessor, the directions to at least one receiver, at least onepossible channel input signal and the sector models collections andweights to output communications to the at least one receiver.

Other implementations of the present disclosure may include a system foroutputting communications to intended receivers via a wave field in apropagating medium, where the system includes providing the directionsto at least one receiver and a structure placed within the propagatingmedium, the structure incorporating multiple transducers generatingconsistent with temporal and spatial Nyquist criteria fluctuating chargeand current densities within the structure within from the transducerinput signals. A directional model relates sets of structure inputsignals to the propagation directions of fields generated in thepropagating medium by the structure's charge and current densityfluctuations. A communications interface is provided for the intendedreceivers, and a processor is communicatively coupled to the structure'stransducer channel inputs and configured for generating their inputsignals, the processor being further configured to use the receiverdirections and the directional model to generate the channel inputsignals needed to convey the communications to the at least onereceiver.

While preferred embodiments of the invention have been described usingspecific terms, such description is for present illustrative purposesonly, and it is to be understood that changes and variations to suchembodiments, including but not limited to the substitution of equivalentfeatures or parts, and the reversal of various features thereof, may bepracticed by those of ordinary skill in the art without departing fromthe spirit or scope of the following claims.

The invention claimed is:
 1. A method for determining directions to andoutputting communications from at least one source contributing to asource wave field in a propagating medium, the method comprising:providing a structure placed within the propagating medium, thestructure incorporating multiple transducers whose output channelsoutput simultaneous signals consistent with temporal and spatial Nyquistcriteria that represent and characterize fluctuating charge and currentdensities within the structure; providing a directional model defining amap between the direction to each possible source in the propagationmedium and a set of output signals created by the fluctuating charge andcurrent densities generated by the waves emanating from each possiblesource in the propagation medium; providing detection criteria fordetermining the presence of signals from at least one source in thepropagation medium in each output channel; providing a sector modelconstructed from the directional model and detection criteria, thesector model defining collections of possible source directions andcollection weights for each output channel; providing a processorcommunicatively coupled to the signals from the output channels andconfigured for analyzing their signals; and using the processor, thesignals from the output channels, the detection criteria, and the sectormodels collections and weights to identify probable collections ofdirections possibly containing the at least one source in thepropagation medium and/or outputting the communications from the atleast one source.
 2. The method of claim 1, wherein the antennastructure is metallic and the charge and current densities are electriccurrent and charge densities, respectively.
 3. The method of claim 1,wherein the antenna structure is metallic material and the charge andcurrent densities are mass current and density fluctuations,respectively.
 4. The method of claim 1, wherein the antenna structureincludes parasitic elements.
 5. The method of claim 1, furthercomprising: restricting consideration of incoming directions to thosecontained in the identified possible collections of directions; andusing the processor, signals from the output channels, the directionalmodel, and the identified collections of probable directions todetermine the directions to and communications from at least one source,to thereby reduce the time and processing required to obtain theselected information.
 6. A system for determining directions to andoutputting communications from at least one source contributing to asource wave field in a propagation medium, the system comprising: astructure placed within the propagating medium, the structureincorporating multiple transducers whose output channels outputsimultaneous signals consistent with temporal and spatial Nyquistcriteria that represent and characterize fluctuating charge and currentdensities within the structure; a directional model defining a mapbetween the direction to each possible source in the propagation mediumand the set of output signals created by the fluctuating charge andcurrent densities generated by the waves emanating from each possiblesource; detection criteria for determining the presence of signals fromat least one source in the propagation medium in each output channel; asector model constructed from the directional model and detectioncriteria, the sector model defining collections of possible sourcedirections and collection weights for each output channel; and aprocessor communicatively coupled to the signals from the outputchannels and configured to use the signals from the output channels, thedetection criteria, and the sector model collections and weights toidentify and output probable collections of directions possiblycontaining the at least one source in the propagation medium and/oroutputting the communications from the at least one source.
 7. Thesystem of claim 6, wherein the antenna structure is metallic and thecharge and current densities are electric current and charge densities,respectively.
 8. The system of claim 6, wherein the antenna structure ismetallic material and the charge and current densities are mass currentand density fluctuations, respectively.
 9. The system of claim 6,wherein the antenna structure includes parasitic elements.
 10. Thesystem of claim 6, the system further comprising: the processor furtherconfigured to restrict consideration of possible directions to those ofthe identified collections of possible directions, signals from theoutput channels, and the directional model to determine the directionsto and communications from at least one source, to thereby reducerequired processing time and system energy requirements.
 11. A methodfor outputting communications to at least one receiver via a physicalwave field in a propagation medium, the method comprising: providing thedirections to the at least one receiver, providing a structure placedwithin the propagating medium, the structure incorporating multipletransducers generating consistent with temporal and spatial Nyquistcriteria fluctuating charge and current densities within the structurefrom the transducer input signals; providing a directional modelrelating input signal sets to the propagation directions of consequentfields generated by said fluctuating charge and current densities withinthe structure; providing a sector model constructed from the directionalmodel, the sector model defining collections of possible receiverdirections and collection weights for each channel, providing aprocessor communicatively coupled to the structure's channel inputs andconfigured for generating their signals; and using the processor, thedirections to at least one receiver, at least one possible channel inputsignal and the sector models collections and weights to outputcommunications to the at least one receiver.
 12. The method of claim 11,wherein the antenna structure is metallic and the charge and currentdensities are electric current and charge densities, respectively. 13.The method of claim 11, wherein the antenna structure is metallicmaterial and the charge and current densities are mass current densityand mass density fluctuations, respectively.
 14. The method of claim 11,wherein the antenna structure includes parasitic elements.
 15. A systemfor outputting communications to intended receivers via a wave field ina propagating medium, the system comprising: providing the directions toat least one receiver, a structure placed within the propagating medium,the structure incorporating multiple transducers generating consistentwith temporal and spatial Nyquist criteria fluctuating charge andcurrent densities within the structure within from the transducer inputsignals; a directional model relating sets of structure input signals tothe propagation directions of fields generated in the propagating mediumby the structure's charge and current density fluctuations; acommunications interface for the intended receivers; and a processorcommunicatively coupled to the structure's transducer channel inputs andconfigured for generating their input signals, the processor beingfurther configured to use the receiver directions and the directionalmodel to generate the channel input signals needed to convey thecommunications to the at least one receiver.
 16. The system of claim 15,wherein the antenna structure is metallic and the charge and currentdensities are electric current and charge densities, respectively. 17.The system of claim 15, wherein the antenna structure is material andthe charge and current densities are mass current density and massdensity fluctuations.
 18. The system of claim 15, wherein the antennastructure includes parasitic elements.